The flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. The flu virus spreads mainly by tiny droplets made when people with flu cough, sneeze, or talk. Learn about the symptoms of flu as well as its diagnosis and treatment.
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Flu
What is the flu?
The flu, also called influenza, is a respiratory infection caused by viruses. Each year, millions of Americans get sick with the flu. Sometimes it causes mild illness. But it can also be serious or even deadly, especially for people over 65, newborn babies, and people with certain chronic illnesses.
What causes the flu?
The flu is caused by flu viruses that spread from person to person. When someone with the flu coughs, sneezes, or talks, they spray tiny droplets. These droplets can land in the mouths or noses of people who are nearby. Less often, a person may get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose, or possibly their eyes.
What are the symptoms of the flu?
Symptoms of the flu come on suddenly and may include:
Fever or feeling feverish/chills
Cough
Sore throat
Runny or stuffy nose
Muscle or body aches
Headaches
Fatigue (tiredness)
Some people may also have vomiting and diarrhea. This is more common in children.
Sometimes people have trouble figuring out whether they have a cold or the flu. There are differences between them. The symptoms of a cold usually come on more slowly and are less severe than symptoms of the flu. Colds rarely cause a fever or headaches.
Sometimes people say that they have a "flu" when they really have something else. For example, "stomach flu" isn't the flu; it's gastroenteritis.
What other problems can the flu cause?
Some people who get the flu will develop complications. Some of these complications can be serious or even life-threatening. They include:
Bronchitis
Ear infection
Sinus infection
Pneumonia
Inflammation of the heart (myocarditis), brain (encephalitis), or muscle tissues (myositis, rhabdomyolysis)
The flu also can make chronic health problems worse. For example, people with asthma may have asthma attacks while they have flu.
Certain people are more likely to have complications from the flu, including:
Adults 65 and older
Pregnant women
Children younger than 5
People with certain chronic health conditions, such as asthma, diabetes, and heart disease
How is the flu diagnosed?
To diagnose the flu, health care providers will first do a medical history and ask about your symptoms. There are several tests for the flu. For the tests, your provider will swipe the inside of your nose or the back of your throat with a swab. Then the swab will be tested for the flu virus.
Some tests are quick and give results in 15-20 minutes. But these tests are not as accurate as other flu tests. These other tests can give you the results in one hour or several hours.
What are the treatments for the flu?
Most people with the flu recover on their own without medical care. People with mild cases of the flu should stay home and avoid contact with others, except to get medical care.
But if you have symptoms of flu and are in a high risk group or are very sick or worried about your illness, contact your health care provider. You might need antiviral medicines to treat your flu. Antiviral medicines can make the illness milder and shorten the time you are sick. They also can prevent serious flu complications. They usually work best when you start taking them within 2 days of getting sick.
Can the flu be prevented?
The best way to prevent the flu is to get flu vaccine every year. But it's also important to have good health habits like covering your cough and washing your hands often. This can help stop the spread of germs and prevent the flu.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (24)
Influenza animation - flu virus mechanism
Video by David Hager/YouTube
WHO: Influenza, an Unpredictable Threat
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SwineFlu Influenza H1N1 Mechanism of Action MOA Animation
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Influenza A and B Infection and Replication
Video by macrophage/YouTube
Influenza: Get the (Antigenic) Drift
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What is influenza?
Video by World Health Organization (WHO)/YouTube
What is Influenza? - Pig Flu - Bird Flu - Human Flu?
Tamiflu Drug for Influenza: Side Effects, Dosage, & Usage
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Could the 1918 Influenza Pandemic Happen Again?
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How to Care for Someone with Influenza
Video by Stanford Health Care/YouTube
Influenza A (H3N2)
Colorized transmission electron micrograph of influenza A virus particles, colorized red and gold, isolated from a patient sample and then propagated in cell culture. Influenza A can infect both humans and animals, including birds and pigs.
More specifically, this image features the H3N2 influenza strain, isolated from a patient in Victoria, Australia, in 1975. Notable for forming both spherical particles/virions (pictured) and filamentous virions, this historical strain can be employed to study the breadth of the immune response elicited by universal flu vaccine candidates.
Image by NIAID/Microscopy by John Gallagher and Audray Harris, NIAID Laboratory of Infectious Diseases.
4:13
Influenza animation - flu virus mechanism
David Hager/YouTube
14:03
WHO: Influenza, an Unpredictable Threat
World Health Organization (WHO)/YouTube
2:15
SwineFlu Influenza H1N1 Mechanism of Action MOA Animation
Scientific Animations/YouTube
3:27
Influenza A and B Infection and Replication
macrophage/YouTube
2:53
Influenza: Get the (Antigenic) Drift
NIAID/YouTube
2:40
What is influenza?
World Health Organization (WHO)/YouTube
3:24
What is Influenza? - Pig Flu - Bird Flu - Human Flu?
Tamiflu Drug for Influenza: Side Effects, Dosage, & Usage
FindaTopDoc Media/YouTube
3:48
Could the 1918 Influenza Pandemic Happen Again?
NIAID/YouTube
2:13
How to Care for Someone with Influenza
Stanford Health Care/YouTube
Influenza A (H3N2)
NIAID/Microscopy by John Gallagher and Audray Harris, NIAID Laboratory of Infectious Diseases.
Overview
Flu Virus Rotation
Image by TheVisualMD
Flu Virus Rotation
The flu (influenza) is large family of viruses that affects birds and mammals and tends to be seasonal, usually beginning in late fall and ending in early spring. Like the common cold (caused by a different family of viruses), respiratory flu infection is widespread, affecting tens of millions in the U.S. each year. Some flu tests detect the influenza virus, while other tests detect the presence of antibodies produced by the body's immune system. There are different types and strains of influenza (including those known as bird or swine flu). Influenza (the flu) is a viral respiratory infection that affects 30 to 50 million Americans and is usually seasonal, beginning in late fall and disappearing in early spring. It is a common respiratory illness that affects 30 to 50 million Americans, especially the very young, elderly, those who are pregnant, with compromised immune systems or pre-existing lung disease each season.
Image by TheVisualMD
Overview of Flu Virus
What is Influenza (also called Flu)?
The flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is by getting a flu vaccine each year.
How Flu Spreads
Most experts believe that flu viruses spread mainly by tiny droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby. Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose or possibly their eyes.
Period of Contagiousness
You may be able to spread flu to someone else before you know you are sick, as well as while you are sick.
People with flu are most contagious in the first 3-4 days after their illness begins.
Some otherwise healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick.
Some people, especially young children and people with weakened immune systems, might be able to infect others for an even longer time.
Onset of Symptoms
The time from when a person is exposed and infected with flu to when symptoms begin is about 2 days, but can range from about 1 to 4 days.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (26)
What is influenza?
Video by World Health Organization (WHO)/YouTube
H1N1 Influenza - What the Public Should Know
Video by CHOC Children's/YouTube
Influenza: An Update on the Disease and Laboratory Diagnosis [Hot Topic]
Video by Mayo Clinic Laboratories/YouTube
How Seasonal Influenza Viruses Evolves
Video by DCODE by Discovery/YouTube
What Was the 1918 Influenza Pandemic?
Video by NIAID/YouTube
How Influenza Pandemics Occur
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Baloxavir Marboxil for Uncomplicated Influenza in Adults and Adolescents
Video by NEJMvideo/YouTube
Baloxavir, oseltamivir similar for influenza
Video by MDedge: news and insights for busy physicians/YouTube
Cold vs. flu symptoms: How to tell if it’s influenza
Video by syracuse.com/YouTube
Influenza: Diagnosis and Treatment
Video by RWJF Microbiology, Immunology & Infectious Diseases/YouTube
Complications of Influenza
Video by Prince Edward Island Government/YouTube
Science Behind The News: Influenza & Flu Vaccines
Video by National Science Foundation/YouTube
Canine Influenza: What You Need to Know | National Geographic
Video by National Geographic/YouTube
Science Bulletins: Influenza—Jumping the Species Barrier
Video by American Museum of Natural History/YouTube
Influenza Treatment - Medications and Criteria for Treatment
macrophage/YouTube
4:39
Influenza, coronavirus and emerging viruses : control and prevention
Prevention & Infection Control/YouTube
0:38
Flu Facts with Dr. Dan - Is the stomach flu caused by the same virus as influenza?
Lakeridge Health/YouTube
12:47
What is the flu? | Infectious diseases | Health & Medicine | Khan Academy
khanacademymedicine/YouTube
4:53
Cold vs. Flu: What's The Difference?
Seeker/YouTube
6:40
What is Highly Pathogenic Avian Influenza?
Penn State Extension/YouTube
25:00
Avian Flu (full documentary)
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4:13
Influenza and Sepsis: Mayo Expert Describes Warning Signs of Severe Sepsis, Septic Shock
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1:41
Sanofi – Influenza Episode 1
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4:43
Influenza Hemagglutinin - Stephen Harrison (Harvard/HHMI)
iBiology Techniques/YouTube
Influenza (Flu)
Influenza Virus
Image by CDC/ Douglas E. Jordan; Photo credit: Illustrator: Dan Higgins
Influenza Virus
This 3-dimensional (3D) image illustrates the very beginning stages of an influenza (flu) infection. Most experts think that influenza viruses spread mainly through small droplets containing influenza virus. These droplets are expelled into the air when people infected with the flu, cough, sneeze or talk. Once in the air, these small infectious droplets can land in the mouths or noses of people who are nearby. This image shows what happens after these influenza viruses enter the human body. The viruses attach to cells within the nasal passages and throat (i.e., the respiratory tract).The influenza virus’s hemagglutinin (HA) surface proteins then bind to the sialic acid receptors on the surface of a human respiratory tract cell. The structure of the influenza virus’s HA surface proteins is designed to fit the sialic acid receptors of the human cell, like a key to a lock. Once the key enters the lock, the influenza virus is then able to enter and infect the cell. This marks the beginning of a flu infection.See PHIL 15325, for this image with no labels, and PHIL 15327, for both its labels and accompanying text. The cut-out box shows a close-up view of how an influenza virus’s HA surface protein binds to a sialic acid on the surface of a human respiratory tract cell.
Image by CDC/ Douglas E. Jordan; Photo credit: Illustrator: Dan Higgins
Influenza (Flu)
Commonly known as the flu, influenza is a common viral disease caused by an orthomyxovirus that primarily affects the upper respiratory tract but can also extend into the lower respiratory tract. Influenza is pervasive worldwide and causes 3,000–50,000 deaths each year in the United States. The annual mortality rate can vary greatly depending on the virulence of the strain(s) responsible for seasonal epidemics.
Influenza infections are most typically characterized by fever, chills, and body aches. This is followed by symptoms similar to the common cold that may last a week or more. Table 22.2 compares the signs and symptoms of influenza and the common cold.
Comparing the Common Cold and Influenza
Sign/Symptom
Common Cold
Influenza
Fever
Low (37.2 °C [99 °F])
High (39 °C [102.2 °F])
Headache
Common
Common
Aches and pains
Mild
Severe
Fatigue
Slight
Severe
Nasal congestion
Common
Rare
Sneezing
Common
Rare
Table 22.2
In general, influenza is self-limiting. However, serious cases can lead to pneumonia and other complications that can be fatal. Such cases are more common in the very young and the elderly; however, certain strains of influenza virus (like the 1918–1919 variant discussed later in this chapter) are more lethal to young adults than to the very young or old. Strains that affect young adults are believed to involve a cytokine storm—a positive feedback loop that forms between cytokine production and leukocytes. This cytokine storm produces an acute inflammatory response that leads to rapid fluid accumulation in the lungs, culminating in pulmonary failure. In such cases, the ability to mount a vigorous immune response is actually detrimental to the patient. The very young and very old are less susceptible to this effect because their immune systems are less robust.
A complication of influenza that occurs primarily in children and teenagers is Reye syndrome. This sequela causes swelling in the liver and brain, and may progress to neurological damage, coma, or death. Reye syndrome may follow other viral infections, like chickenpox, and has been associated with the use of aspirin. For this reason, the CDC and other agencies recommend that aspirin and products containing aspirin never be used to treat viral illnesses in children younger than age 19 years.
The influenza virus is primarily transmitted by direct contact and inhalation of aerosols. The RNA genome of this virus exists as seven or eight segments, each coated with ribonucleoprotein and encoding one or two specific viral proteins. The influenza virus is surrounded by a lipid membrane envelope, and two of the main antigens of the influenza virus are the spike proteins hemagglutinin (H) and neuraminidase (N), as shown in Figure 22.17. These spike proteins play important roles in the viral infectious cycle.
Figure 22.17 The illustration shows the structure of an influenza virus. The viral envelope is studded with copies of the proteins neuraminidase and hemagglutinin, and surrounds the individual seven or eight RNA genome segments. (credit: modification of work by Dan Higgins, Centers for Disease Control and Prevention)
Following inhalation, the influenza virus uses the hemagglutinin protein to bind to sialic acid receptors on host respiratory epithelial cells. This facilitates endocytosis of the viral particle. Once inside the host cell, the negative strand viral RNA is replicated by the viral RNA polymerase to form mRNA, which is translated by the host to produce viral proteins. Additional viral RNA molecules are transcribed to produce viral genomic RNA, which assemble with viral proteins to form mature virions. Release of the virions from the host cell is facilitated by viral neuraminidase, which cleaves sialic-acid receptors to allow progeny viruses to make a clean exit when budding from an infected cell.
There are three genetically related influenza viruses, called A, B, and C. The influenza A viruses have different subtypes based on the structure of their hemagglutinin and neuraminidase proteins. There are currently 18 known subtypes of hemagglutinin and 11 known subtypes of neuraminidase. Influenza viruses are serologically characterized by the type of H and N proteins that they possess. Of the nearly 200 different combinations of H and N, only a few, such as the H1N1 strain, are associated with human disease. The influenza viruses A, B, and C make up three of the five major groups of orthomyxoviruses. The differences between the three types of influenza are summarized in Table 22.3. The most virulent group is the influenza A viruses, which cause seasonal pandemics of influenza each year. Influenza A virus can infect a variety of animals, including pigs, horses, and even whales and dolphins. Influenza B virus is less virulent and is sometimes associated with epidemic outbreaks. Influenza C virus generally produces the mildest disease symptoms and is rarely connected with epidemics. Neither influenza B virus nor influenza C virus has significant animal reservoirs.
The Three Major Groups of Influenza Viruses
Influenza A virus
Influenza B virus
Influenza C virus
Severity
Severe
Moderate
Mild
Animal reservoir
Yes
No
No
Genome segments
8
8
7
Population spread
Epidemic and pandemic
Epidemic
Sporadic
Antigenic variation
Shift/drift
Drift
Drift
Table 22.3
Influenza virus infections elicit a strong immune response, particularly to the hemagglutinin protein, which would protect the individual if they encountered the same virus. Unfortunately, the antigenic properties of the virus change relatively rapidly, so new strains are evolving that immune systems previously challenged by influenza virus cannot recognize. When an influenza virus gains a new hemagglutinin or neuraminidase type, it is able to evade the host’s immune response and be successfully transmitted, often leading to an epidemic.
There are two mechanisms by which these evolutionary changes may occur. The mechanisms of antigen drift and antigenic shift for influenza virus have been described in Virulence Factors of Bacterial and Viral Pathogens. Of these two genetic processes, it is viruses produced by antigenic shift that have the potential to be extremely virulent because individuals previously infected by other strains are unlikely to produce any protective immune response against these novel variants.
The most lethal influenza pandemic in recorded history occurred from 1918 through 1919. Near the end of World War I, an antigenic shift involving the recombination of avian and human viruses is thought to have produced a new H1N1 virus. This strain rapidly spread worldwide and is commonly claimed to have killed as many as 40 million to 50 million people—more than double the number killed in the war. Although referred to as the Spanish flu, this disease is thought to have originated in the United States. Regardless of its source, the conditions of World War I greatly contributed to the spread of this disease. Crowding, poor sanitation, and rapid mobilization of large numbers of personnel and animals facilitated the dissemination of the new virus once it appeared.
Several of the most important influenza pandemics of modern times have been associated with antigenic shifts. A few of these are summarized in Table 22.4.
few of these are summarized in Table 22.4.
Historical Influenza Outbreaks
Years
Common Name
Serotype
Estimated Number of Deaths
1918–1919
Spanish flu
H1N1
20,000,000–40,000,000
1957–1958
Asian flu
N2N2
1,000,000–2,000,000
1968–1969
Hong Kong flu
H3N2
1,000,000–3,000,000
2009–2010
Swine flu
H1N1/09
152,000–575,000
Table 22.4
Laboratory diagnosis of influenza is typically performed using a variety of RIDTs. These tests are inoculated by point-of-care personnel and give results within 15–20 minutes. Unfortunately, these tests have variable sensitivity and commonly yield false-negative results. Other tests include hemagglutination of erythrocytes (due to hemagglutinin action) or complement fixation. Patient serum antibodies against influenza viruses can also be detected in blood samples. Because influenza is self-limiting disease, diagnosis through these more time-consuming and expensive methods is not typically used.
Three drugs that inhibit influenza neuraminidase activity are available: inhaled zanamivir, oral oseltamivir, and intravenous peramivir. If taken at the onset of symptoms, these drugs can shorten the course of the disease. These drugs are thought to impair the ability of the virus to efficiently exit infected host cells. A more effective means of controlling influenza outbreaks, though, is vaccination. Every year, new influenza vaccines are developed to be effective against the strains expected to be predominant. This is determined in February by a review of the dominant strains around the world from a network of reporting sites; their reports are used to generate a recommendation for the vaccine combination for the following winter in the northern hemisphere. In September, a similar recommendation is made for the winter in the southern hemisphere. These recommendations are used by vaccine manufacturers to formulate each year’s vaccine. In most cases, three or four viruses are selected—the two most prevalent influenza A strains and one or two influenza B strains. The chosen strains are typically cultivated in eggs and used to produce either an inactivated or a live attenuated vaccine (e.g., FluMist). For individuals 18 years or older with an allergy to egg products, a recombinant egg-free trivalent vaccine is available. Most of the influenza vaccines over the past decade have had an effectiveness of about 50%.
Flu Pandemic
During the spring of 2013, a new strain of H7N9 influenza was reported in China. A total of 132 people were infected. Of those infected, 44 (33%) died. A genetic analysis of the virus suggested that this strain arose from the reassortment of three different influenza viruses: a domestic duck H7N3 virus, a wild bird H7N9 virus, and a domestic poultry H9N2 virus. The virus was detected in the Chinese domestic bird flocks and contact with this reservoir is thought to have been the primary source of infection. This strain of influenza was not able to spread from person to person. Therefore, the disease did not become a global problem. This case does, though, illustrate the potential threat that influenza still represents. If a strain like the H7N9 virus were to undergo another antigenic shift, it could become more communicable in the human population. With a mortality rate of 33%, such a pandemic would be disastrous. For this reason, organizations like the World Health Organization and the Centers for Disease Control and Prevention keep all known influenza outbreaks under constant surveillance.
Source: CNX OpenStax
Additional Materials (2)
8-year-old dies from apparent complications of the flu virus
Video by KSL News/YouTube
Influenza Milestones 1917 – 2009 Timeline
Image by Centers for Disease Control and Prevention (CDC)
2:07
8-year-old dies from apparent complications of the flu virus
KSL News/YouTube
Influenza Milestones 1917 – 2009 Timeline
Centers for Disease Control and Prevention (CDC)
Symptoms
Coughing and respiratory distress
Image by TheVisualMD
Coughing and respiratory distress
Image by TheVisualMD
Flu Symptoms
Influenza (flu) can cause mild to severe illness, and at times can lead to death. Flu is different from a cold. Flu usually comes on suddenly. People who have flu often feel some or all of these symptoms:
fever* or feeling feverish/chills
cough
sore throat
runny or stuffy nose
muscle or body aches
headaches
fatigue (tiredness)
some people may have vomiting and diarrhea, though this is more common in children than adults.
*It’s important to note that not everyone with flu will have a fever.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (5)
Why The Flu Causes Aches & Pains
Video by Seeker/YouTube
Symptoms of H1N1 (Swine Flu)
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Know the common symptoms of flu
Video by Centers for Disease Control and Prevention (CDC)/YouTube
Symptoms of Influenza
Image by Mikael Haggstrom
4:05
Why The Flu Causes Aches & Pains
Seeker/YouTube
3:25
Symptoms of H1N1 (Swine Flu)
Centers for Disease Control and Prevention (CDC)/YouTube
12:47
What is the flu? | Infectious diseases | Health & Medicine | Khan Academy
khanacademymedicine/YouTube
0:37
Know the common symptoms of flu
Centers for Disease Control and Prevention (CDC)/YouTube
Symptoms of Influenza
Mikael Haggstrom
Cold vs Flu
Cold or Flu
Image by niaid
Cold or Flu
The flu and the common cold are both respiratory illnesses but they are caused by different viruses. Because these two types of illnesses have similar flu-like symptoms, it can be difficult to tell the difference between them based on symptoms alone. In general, the flu is worse than the common cold, and symptoms such as fever, body aches, extreme tiredness, and dry cough are more common and intense. Colds are usually milder than the flu. People with colds are more likely to have a runny or stuffy nose. Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations.
Because colds and flu share many symptoms, it can be difficult (or even impossible) to tell the difference between them based on symptoms alone. Special tests that usually must be done within the first few days of illness can be carried out, when needed to tell if a person has the flu.
In general, the flu is worse than the common cold, and symptoms such as fever, body aches, extreme tiredness, and dry cough are more common and intense. Colds are usually milder than the flu. People with colds are more likely to have a runny or stuffy nose. Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations.
CDC
Image by niaid
Cold Versus Flu
What is the difference between a cold and flu?
Influenza (flu) and the common cold are both contagious respiratory illnesses, but they are caused by different viruses. Flu is caused by influenza viruses only, whereas the common cold can be caused by a number of different viruses, including rhinoviruses, parainfluenza, and seasonal coronaviruses. Seasonal coronaviruses should not be confused with SARS-CoV-2, the virus that causes COVID-19. Because flu and the common cold have similar symptoms, it can be difficult to tell the difference between them based on symptoms alone. In general, flu is worse than the common cold, and symptoms are typically more intense and begin more abruptly. Colds are usually milder than flu. People with colds are more likely to have a runny or stuffy nose than people who have flu. Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations. Flu can have serious associated complications.
How can you tell the difference between a cold and flu?
Because colds and flu share many symptoms, it can be difficult (or even impossible) to tell the difference between them based on symptoms alone. Special tests can tell if a person is sick with flu.
What are the symptoms of flu versus the symptoms of a cold?
The symptoms of flu can include fever or feeling feverish/chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, and fatigue (tiredness). Cold symptoms are usually milder than the symptoms of flu. People with colds are more likely to have a runny or stuffy nose. Colds generally do not result in serious health problems.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (1)
How to tell the flu from a cold
Video by Global News/YouTube
6:43
How to tell the flu from a cold
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What To Do If You Get Sick with Flu
Stay home and rest
Image by silviarita/Pixabay
Stay home and rest
Stay home and rest
Image by silviarita/Pixabay
What To Do If You Get Sick with Flu
What should I do if I get sick?
Most people with the flu have mild illness and do not need medical care or antiviral drugs. If you get sick with flu symptoms, in most cases, you should stay home and avoid contact with other people except to get medical care.
If, however, you have symptoms of flu and are in a high risk group, or are very sick or worried about your illness, contact your health care provider (doctor, physician assistant, etc.).
Certain people are at high risk of serious flu-related complications (including young children, people 65 and older, pregnant women and people with certain medical conditions). This is true both for seasonal flu and novel flu virus infections. If you are in a high risk group and develop flu symptoms, it’s best for you to contact your doctor early in your illness. Remind them about your high risk status for flu. CDC recommends that people at high risk for complications should get antiviral treatment as early as possible, because benefit is greatest if treatment is started within 2 days after illness onset.
Do I need to go the emergency room if I am only a little sick?
No. The emergency room should be used for people who are very sick. You should not go to the emergency room if you are only mildly ill.
If you have emergency warning signs of flu sickness, you should go to the emergency room. If you get sick with flu symptoms and are at higher risk of flu complications or you are concerned about your illness, call your health care provider for advice.
What are the emergency warning signs of flu sickness?
People experiencing any of these warning signs should obtain medical care right away.
In children
Fast breathing or trouble breathing
Bluish lips or face
Ribs pulling in with each breath
Chest pain
Severe muscle pain (child refuses to walk)
Dehydration (no urine for 8 hours, dry mouth, no tears when crying)
Not alert or interacting when awake
Seizures
Fever above 104°F
In children less than 12 weeks, any fever
Fever or cough that improve but then return or worsen
Worsening of chronic medical conditions
In adults
Difficulty breathing or shortness of breath
Persistent pain or pressure in the chest or abdomen
Persistent dizziness, confusion, inability to arouse
Seizures
Not urinating
Severe muscle pain
Severe weakness or unsteadiness
Fever or cough that improve but then return or worsen
Worsening of chronic medical conditions
These lists are not all inclusive. Please consult your medical provider for any other symptom that is severe or concerning.
Are there medicines to treat the flu?
Yes. There are drugs your doctor may prescribe for treating the flu called “antivirals.” These drugs can make you better faster and may also prevent serious complications.
How long should I stay home if I’m sick?
CDC recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or other necessities. Your fever should be gone without the need to use a fever-reducing medicine, such as Tylenol ®. Until then, you should stay home from work, school, travel, shopping, social events, and public gatherings.
CDC also recommends that children and teenagers (anyone aged 18 years and younger) who have flu or are suspected to have flu should not be given Aspirin (acetylsalicylic acid) or any salicylate containing products (e.g. Pepto Bismol); this can cause a rare, very serious complication called Reye’s syndrome.
What should I do while I’m sick?
Stay away from others as much as possible to keep from infecting them. If you must leave home, for example to get medical care, wear a facemask if you have one, or cover coughs and sneezes with a tissue. Wash your hands often to keep from spreading flu to others.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (2)
What Should You Do If You Get Flu?
Video by Centers for Disease Control and Prevention (CDC)/YouTube
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What Should You Do If You Get Flu?
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FAQs About the New Flu
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Complications
Normal Myocardium / Inflammation of the Myocardium (Myocarditis)
Normal Heart vs Myocarditis
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Normal Myocardium / Inflammation of the Myocardium (Myocarditis)
Normal Heart vs Myocarditis
1) Normal Heart
2) Myocarditis (inflammation of the heart) from COVID-19
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Flu Complications
Flu Complications
Most people who get flu will recover in a few days to less than two weeks, but some people will develop complications (such as pneumonia) as a result of flu, some of which can be life-threatening and result in death.
Sinus and ear infections are examples of moderate complications from flu, while pneumonia is a serious flu complication that can result from either influenza virus infection alone or from co-infection of flu virus and bacteria. Other possible serious complications triggered by flu can include inflammation of the heart (myocarditis), brain (encephalitis) or muscle (myositis, rhabdomyolysis) tissues, and multi-organ failure (for example, respiratory and kidney failure). Flu virus infection of the respiratory tract can trigger an extreme inflammatory response in the body and can lead to sepsis, the body’s life-threatening response to infection. Flu also can make chronic medical problems worse. For example, people with asthma may experience asthma attacks while they have flu, and people with chronic heart disease may experience a worsening of this condition triggered by flu.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (2)
What are the warning signs of flu complications?
Video by Vanderbilt Health/YouTube
Infectious Diseases A-Z: Complications from the flu can be fatal
Video by Mayo Clinic/YouTube
1:47
What are the warning signs of flu complications?
Vanderbilt Health/YouTube
1:08
Infectious Diseases A-Z: Complications from the flu can be fatal
3D visualization of a midsagittal view of the upper respiratory tract, paranasal sinuses and oral cavity reconstructed from scanned human data. When air is inhaled into the lungs, it flows through large tubes called bronchi, branches into smaller tubes known as bronchioles, and ends up in the thousands of small pouches that are the alveoli. This is where the oxygen is transferred from the air into the bloodstream. Each alveolar sac, or air sac, is surrounded by a bed of capillaries, and the walls between the lung and the capillary are extremely thin. The walls are so delicate, in fact, that the inhaled oxygen can seep from the air sacs to bind to the hemoglobin in the blood, while the carbon dioxide and other waste gasses leave the blood and diffuse into the lungs where they can be exhaled.
Interactive by TheVisualMD
People at Higher Risk of Flu Complications
Anyone can get sick with flu, even healthy people, and serious problems related to flu can happen to anyone at any age, but some people are at higher risk of developing serious flu-related complications if they get sick. This includes people 65 years and older, people of any age with certain chronic medical conditions (such as asthma, diabetes, or heart disease), pregnant people and children younger than 5 years, but especially those younger than 2 years old.
Following is a list of all the health and age factors that are known to increase a person’s risk of getting serious complications from flu:
Adults 65 years and older
Children younger than 2 years old
Asthma
Neurologic and neurodevelopment conditions
Blood disorders (such as sickle cell disease)
Chronic lung disease (such as chronic obstructive pulmonary disease [COPD] and cystic fibrosis)
Endocrine disorders (such as diabetes mellitus)
Heart disease (such as congenital heart disease, congestive heart failure and coronary artery disease)
Kidney diseases
Liver disorders
Metabolic disorders (such as inherited metabolic disorders and mitochondrial disorders)
People who are obese with a body mass index [BMI] of 40 or higher
People younger than 19 years old on long-term aspirin- or salicylate-containing medications.
People with a weakened immune system due to disease (such as people with HIV or AIDS, or some cancers such as leukemia) or medications (such as those receiving chemotherapy or radiation treatment for cancer, or persons with chronic conditions requiring chronic corticosteroids or other drugs that suppress the immune system)
People who have had a stroke
Other people at higher risk from flu:
Pregnant people and people up to 2 weeks after the end of pregnancy
People who live in nursing homes and other long-term care facilities
People from certain racial and ethnic minority groups are at increased risk for hospitalization with flu, including non-Hispanic Black persons, Hispanic or Latino persons, and American Indian or Alaska Native persons
Although all children younger than 5 years old are considered at higher risk of serious flu complications, the highest risk is for those younger than 2 years old, with the highest hospitalization and death rates among infants younger than 6 months old.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (4)
Flu Season Slams Seniors
Video by Lee Health/YouTube
High-dose flu vaccine for seniors could save lives | What She Said
Video by WhatSheSaid Talk/YouTube
8-year-old dies from apparent complications of the flu virus
Video by KSL News/YouTube
Influenza: Get the (Antigenic) Drift
Video by NIAID/YouTube
1:54
Flu Season Slams Seniors
Lee Health/YouTube
9:53
High-dose flu vaccine for seniors could save lives | What She Said
WhatSheSaid Talk/YouTube
2:07
8-year-old dies from apparent complications of the flu virus
KSL News/YouTube
2:53
Influenza: Get the (Antigenic) Drift
NIAID/YouTube
Diagnosis
Chest X-ray in influenza and Haemophilus influenzae
Image by Mikael Häggström
Chest X-ray in influenza and Haemophilus influenzae
Chest X-ray of a 76 year old woman, who developed cough and labored breathing. First testing showed influenza B virus, and later a nasopharyngeal swab detected Haemophilus influenzae. The H influenzae presumably developed as an opportunistic infection secondary to the flu. This X-ray was taken 2 weeks after cultures and start of antibiotics, showing delayed pneumonic infiltrates that were only vaguely visible on initial (not shown) X-rays.
Image by Mikael Häggström
Diagnosis of Flu
How do I know if I have the flu?
Your respiratory illness might be influenza (flu) if you have fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and/or fatigue. Some people may have vomiting and diarrhea, though this is more common in children. People may be sick with flu and have respiratory symptoms without a fever. Flu viruses usually cause the most illness during the colder months of the year. However, flu can also occur outside of the typical flu season. In addition, other viruses can also cause respiratory illness similar to flu. So, it is impossible to tell for sure if you have flu based on symptoms alone. If your doctor needs to know for sure whether you are sick with flu, there are laboratory tests that can be done.
What kinds of flu tests are there?
A number of tests are available to detect flu viruses in respiratory specimens. The most common are called “rapid influenza diagnostic tests (RIDTs).” RIDTs work by detecting the parts of the virus (antigens) that stimulate an immune response. These tests can provide results within approximately 10-15 minutes but may not be as accurate as other flu tests. Therefore, you could still have flu, even though your rapid test result is negative. Other flu tests called “rapid molecular assays” detect genetic material of the flu virus. Rapid molecular assays produce results in 15-20 minutes and are more accurate than RIDTs.
In addition to RIDTs and rapid molecular assays, there are several more accurate flu tests available that must be performed in specialized laboratories, such as those found in hospitals or public health laboratories. These tests include reverse transcription polymerase chain reaction (RT-PCR), viral culture, and immunofluorescence assays. All of require that a health care provider swipe the inside of your nose or the back of your throat with a swab and then send the swab for testing. Results may take one to several hours.
How well can rapid tests detect the flu?
During a flu outbreak, a positive rapid flu test is likely to indicate flu virus infection. However, rapid tests vary in their ability to detect flu viruses, depending on the type of rapid test used, and on the type of flu viruses circulating. Also, rapid tests appear to be better at detecting flu in children than in adults. This variation in ability to detect viruses can result in some people who are infected with flu having a negative rapid test result. This situation is called a false negative test result. Despite a negative rapid test result, your health care provider may diagnose you with flu based on your symptoms and their clinical judgment.
Will my health care provider test me for flu if I have flu-like symptoms?
While your doctor may test you for flu, not everyone who goes to the doctor with flu-like symptoms will be tested. After evaluating you, your doctor may choose to diagnose you with flu without the need for testing based on your symptoms and his or her own clinical judgement.
Can I have flu and COVID-19 at the same time?
Yes. It is possible to have flu as well as other respiratory illnesses including COVID-19 at the same time. Health experts are still studying how common this can be.
Some of the symptoms of flu and COVID-19 are similar, making it hard to tell the difference between them based on symptoms alone. Diagnostic testing can help determine if you are sick with flu, COVID-19, or another respiratory infection.
Is there a test that can detect both flu and COVID-19?
Yes. There is a test that will check for seasonal flu type A and B viruses and SARS-CoV-2, the virus that causes COVID-19. This test is being used by U.S. public health laboratories for surveillance purposes. Testing for these viruses at the same time will give public health officials important information about how flu and COVID-19 are spreading and what prevention steps should be taken. The test will also help public health laboratories save time and testing materials, and to possibly return test results faster.
The Food and Drug Administration (FDA) has given CDC an Emergency Use Authorization for this new test. Initial test kits were sent to public health laboratories in early August 2020. CDC will continue to manufacture and distribute these kits.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (3)
Flu Symptoms and Diagnosis
Video by khanacademymedicine/YouTube
All you need to know about the flu and influenza tests
Video by Pathology Tests Explained/YouTube
Testing for the flu | Infectious diseases | Health & Medicine | Khan Academy
Video by khanacademymedicine/YouTube
4:26
Flu Symptoms and Diagnosis
khanacademymedicine/YouTube
4:53
All you need to know about the flu and influenza tests
Pathology Tests Explained/YouTube
8:58
Testing for the flu | Infectious diseases | Health & Medicine | Khan Academy
A flu (influenza) test checks to see if you have the flu, so you can get treated sooner. Early treatment may help lessen the symptoms of the flu. A number of flu tests are available to detect the presence of influenza viruses.
A flu (influenza) test checks to see if you have the flu, so you can get treated sooner. Early treatment may help lessen the symptoms of the flu. A number of flu tests are available to detect the presence of influenza viruses.
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Use the slider below to see how your results affect your
health.
Your result is Negative.
A negative result means that the test did not detect any influenza viral antigen.
Related conditions
Influenza, known as the flu, is a respiratory infection caused by a virus. The flu virus usually spreads from person to person through coughing or sneezing. You can also get the flu by touching a surface that has the flu virus on it, and then touching your own nose or eyes.
The flu is most common during certain times of the year, known as flu season. In the United States, flu season can begin as early as October and end as late as May. During each flu season, millions of Americans get the flu. Most people who get the flu will feel sick with muscle aches, fever, and other uncomfortable symptoms, but will recover within a week or so. For others, the flu can cause very serious illness, and even death.
A flu test can help your health care provider figure out if you have the flu, so you can get treated earlier. Early treatment may help lessen the symptoms of the flu. There are a few different types of flu tests. The most common is called the rapid influenza antigen test, or rapid influenza diagnostic test. This type of test can provide results in less than half an hour, but is not as accurate as some other types of flu tests. More sensitive tests may require your health care provider to send samples to a specialized lab.
Flu tests are used to help figure out whether you have the flu. Flu tests are also sometimes used to:
Figure out whether an outbreak of respiratory illness in a community, such as a school or nursing home, has been caused by the flu.
Identify the type of flu virus that is causing infections. There are three main types of flu viruses: A, B, and C. Most seasonal flu outbreaks are caused by the A and/or B flu viruses.
You may or may not need a flu test, depending on your symptoms and risk factors. Symptoms of the flu include:
Fever
Chills
Muscle aches
Weakness
Headache
Stuffy nose
Sore throat
Cough
Even if you have flu symptoms, you may not need a flu test, because many cases of the flu don't need special treatment. Your health care provider may order a flu test if you have risk factors for flu complications. You may be at a higher risk for serious illness from the flu if you:
Have a weakened immune system
Are pregnant
Are over the age of 65
Are under the age of 5
Are in the hospital
There are a couple of different ways to get a sample for testing:
Swab test. Your health care provider will use a special swab to take a sample from your nose or throat.
Nasal Aspirate. Your health care provider will inject a saline solution into your nose, then remove the sample with gentle suction.
You don't need any special preparations for a flu test.
You may feel a gagging sensation or even a tickle when your throat or nose is swabbed. The nasal aspirate may feel uncomfortable. These effects are temporary.
A positive result means you may have the flu. Your health care provider may prescribe medicine to help prevent flu complications. A negative result means you likely don't have the flu, and that some other virus is probably causing your symptoms. Your health care provider may order more tests before making a diagnosis. If you have questions about your results, talk to your health care provider.
Most people recover from the flu within a week or two, whether or not they take flu medicine. So you probably won't need a flu test, unless you are at risk for flu complications.
https://medlineplus.gov/lab-tests/flu-influenza-test/ [accessed on Oct 16, 2019]
https://labtestsonline.org/tests/influenza-tests [accessed on Oct 16, 2019]
https://www.cdc.gov/flu/professionals/diagnosis/clinician_guidance_ridt.htm [accessed on Oct 16, 2019]
Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."
Additional Materials (50)
Influenza A virus
H1N1 virus : This colorized transmission electron micrograph shows H1N1 influenza virus particles. National Institute of Allergy and Infectious Diseases (NIAID)
Image by (NIH) (NIAID)
Influenza A virus
This digitally-colorized, negative-stained transmission electron microscopic (TEM) image depicted a number of Influenza A virions.
Image by CDC/ F. A. Murphy
Influenza A virus
H1N1 Influenza Virus Particles : Colorized transmission electron micrograph showing H1N1 influenza virus particles. Surface proteins on the virus particles are shown in black.
Image by NIAID
Influenza Virus
This 3-dimensional (3D) image illustrates the very beginning stages of an influenza (flu) infection. Most experts think that influenza viruses spread mainly through small droplets containing influenza virus. These droplets are expelled into the air when people infected with the flu, cough, sneeze or talk. Once in the air, these small infectious droplets can land in the mouths or noses of people who are nearby. This image shows what happens after these influenza viruses enter the human body. The viruses attach to cells within the nasal passages and throat (i.e., the respiratory tract).
The influenza virus’s hemagglutinin (HA) surface proteins then bind to the sialic acid receptors on the surface of a human respiratory tract cell. The structure of the influenza virus’s HA surface proteins is designed to fit the sialic acid receptors of the human cell, like a key to a lock. Once the key enters the lock, the influenza virus is then able to enter and infect the cell. This marks the beginning of a flu infection.
Image by CDC/ Douglas E. Jordan; Photo credit: Illustrator: Dan Higgins
Influenza Virus
On a dark-blue background, this illustration provides a 3D graphical representation of a generic influenza virion's ultrastructure, and is not specific to a seasonal, avian or 2009 H1N1 virus. A portion of the virion's outer protein coat has been cut away, which reveals the virus' contents, and a key has been included, which identifies these components. See PHIL 11877 for an uncut view of the virion's exterior.
Image by CDC
Woman receiving nasal flu vaccine
This 2009 image depicts a healthcare practitioner as he was administering the H1N1 live attenuated intranasal vaccine (LAIV) to an Indian female recipient. Using a small syringe, he was delivering the vaccine mist into the woman’s right nostril.
Image by CDC/ Dr. Bill Atkinson; Photo credit: James Gathany
Influenza virus
This negatively-stained transmission electron micrograph (TEM) revealed the presence of a number of influenza virus virions. This virus is a Orthomyxoviridae virus family member.
Image by CDC
Avian influenza
Bird Flu Virus Picture Colorized transmission electron micrograph of Avian influenza A H5N1 viruses (seen in gold) grown in MDCK cells (seen in green). Avian influenza A viruses do not usually infect humans; however, several instances of human infections and outbreaks have been reported since 1997. When such infections occur, public health authorities monitor these situations closely.
Image by CDC/ Courtesy of Cynthia Goldsmith; Jacqueline Katz; Sherif R. Zaki
Sneezing
Sneezing : The delicate operation of catching a cold on a photo.
Image by AnA oMeLeTe from Faro, Portugal
Vaccination
This photograph showed a nurse in the process of administering a vaccination to a young girl into her left shoulder muscle, while her younger sister observed from behind.
Image by CDC
Hong Kong flu
This negatively-stained transmission electron micrograph (TEM) revealed the presence of a number of Hong Kong flu virus virions, the H3N2 subtype of the influenza A virus. This virus is a Orthomyxoviridae virus family member, and was responsible for the flu pandemic of 1968-1969, which infected an estimated 50,000,000 people in the United States, killing 33,000. Note the proteinaceous coat, or capsid, surrounding each virion, and the hemagglutinin-neuraminidase spikes, which differ in terms of their molecular make-up from strain to strain.
Image by CDC
Immunization
Infant Receiving Immunization from Nurse: Held by his mother, this infant was receiving an intramuscular immunization in his left thigh muscle, which was being administered by a qualified nurse who was stabilizing the injection site with her palm. The nurse was distracting the infant while she was administering the vaccine.
Image by CDC
Influenza A (H1N1) virus
Digitally-colorized transmission electron microscopic image of spherical virions from a 2009 pandemic influenza A (H1N1) virus isolate, which are surrounded by distinct spikes.
Image by CDC/ C. S. Goldsmith and A. Balish
Vaccination
Image by BruceBlaus
A nurse vaccinates Barack Obama against H1N1
A White House nurse prepares to administer the H1N1 vaccine to President Barack Obama at the White House.
Image by White House (Pete Souza)/Wikimedia
Neuraminidase inhibitor
Machanism of Neuraminidase inhibitor
Image by Phs2014
Neuraminidase - Structure of the neuraminidase from the H1N1 1918 pandemic influenza virus.
Image by TimVickers
human immunodeficiency virus (HIV)
HIV. See a full animation of this medical topic
Image by BruceBlaus
Cytokine Storm Mechanism
Proposed Mechanism of the Cytokine Storm Evoked by Influenzavirus. The key element in generating the storm is an uncontrolled exuberant immune response to the virus, in which there is an outpouring of proinflammatory cytokines and chemoattractants.
Image by GrrlScientist/NEJM
Influenza Specimen Collection
A nasopharyngeal (NP) swab is the optimal upper respiratory tract specimen collection method for influenza testing.
Document by Centers for Disease Control and Prevention (CDC)
Nasopharyngeal swab
This diagnostic method is commonly used in suspected cases of whooping cough, diphtheria, influenza, and various types of diseases caused by the coronavirus family of viruses, including SARS, MERS, and COVID-19.
Image by cdc.gov/Wikimedia
All you need to know about the flu and influenza tests
Video by Pathology Tests Explained/YouTube
Influenza animation - flu virus mechanism
Video by David Hager/YouTube
avian influenza
Video by Murat BALABAN/YouTube
WHO: Influenza, an Unpredictable Threat
Video by World Health Organization (WHO)/YouTube
The H1N1 Swine Flu: A Look Inside
Video by Discovery/YouTube
What Is an Inner Ear Infection? | Ear Problems
Video by Howcast/YouTube
ear infections in adults
Video by midnightfocus/YouTube
SwineFlu Influenza H1N1 Mechanism of Action MOA Animation
Video by Scientific Animations/YouTube
Symptoms of H1N1 (Swine Flu)
Video by Centers for Disease Control and Prevention (CDC)/YouTube
How to Prevent & Recognize Symptoms of Swine Flu
Video by Howcast/YouTube
Influenza: Get the (Antigenic) Drift
Video by NIAID/YouTube
What is Influenza? - Pig Flu - Bird Flu - Human Flu?
5 common flu vaccine excuses | Infectious diseases | Health & Medicine | Khan Academy
khanacademymedicine/YouTube
1:18
Flu Vaccine for Children & Flu Shot Side Effects
Cleveland Clinic/YouTube
1:59
Bird Flu - Causes, Symptoms, Treatments & More…
Rehealthify/YouTube
12:47
What is the flu? | Infectious diseases | Health & Medicine | Khan Academy
khanacademymedicine/YouTube
3:48
How Flu Viruses Attack National Geographic
maia86magnoly/YouTube
3:35
How The Flu Shot Works (And Why You Should Get It)
Seeker/YouTube
3:11
The Flu Vaccine 101
Science Filmmaking Tips/YouTube
0:41
Why does being pregnant put me at a higher risk for flu?
U.S. Department of Health and Human Services/YouTube
2:47
Hib (Haemophilus influenzae type b)
yakimahealthdistrict/YouTube
8:16
Three types of flu | Infectious diseases | Health & Medicine | Khan Academy
khanacademymedicine/YouTube
7:12
When flu viruses attack! | Infectious diseases | Health & Medicine | Khan Academy
khanacademymedicine/YouTube
3:39
Flu Attack! How A Virus Invades Your Body | Krulwich Wonders | NPR
NPR/YouTube
Nasal Swab Test
Nasal Swab Test
Also called: Nasopharyngeal culture, Nasopharyngeal swab, NP swab
A nasal swab is a test that takes a sample of cells from the nasopharynx (the uppermost part of your nose and throat). It is used to diagnose respiratory infections.
Nasal Swab Test
Also called: Nasopharyngeal culture, Nasopharyngeal swab, NP swab
A nasal swab is a test that takes a sample of cells from the nasopharynx (the uppermost part of your nose and throat). It is used to diagnose respiratory infections.
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Use the slider below to see how your results affect your
health.
Your result is Negative.
A negative result means no harmful viruses or bacteria were found in your sample.
Related conditions
A nasal swab, also called a nasopharyngeal culture, is a test that checks for viruses and bacteria that cause respiratory infections. The test is done by taking a sample of cells from the uppermost part of your nose and throat. This area is known as the nasopharynx.
There are many types of respiratory infections. The test can help your provider diagnose the type of infection you have and which treatment would be best for you.
A nasal swab is used to diagnose certain infections of the respiratory system. These include:
The flu
COVID-19 infections
Respiratory syncytial virus (RSV). This is a common and usually mild respiratory infection. But it can be dangerous to young babies and older adults.
Whooping cough, a bacterial infection that causes severe fits of coughing and trouble breathing
Meningitis, a disease caused by inflammation of the membranes that surround the brain and spinal cord
MRSA (methicillin-resistant Staphylococcus aureus), a serious type of bacterial infection that can be very difficult to treat
You may need this test if you have symptoms of a respiratory infection. These include:
Cough
Fever
Stuffy or runny nose
Sore throat
Headache
Fatigue
Muscle aches
During the test:
You will tip your head back.
Your health care provider will insert a swab into your nostril until it reaches your nasopharynx (the upper part of your throat).
Your provider will rotate the swab to collect the sample
Your provider will remove the swab.
You don't need any special preparations for a nasal swab.
The test may tickle your throat or cause you to cough. These effects are temporary.
Depending on your symptoms, you may have been tested for one or more types of infections.
A negative result means no harmful viruses or bacteria were found in your sample.
A positive result means a specific type of harmful virus or bacteria was found in your sample. It indicates you have a specific type of infection. If you are diagnosed with an infection, be sure to follow your provider's recommendations for treating your illness. This may include medicines and steps to prevent spreading the infection to others.
Nasopharyngeal culture: MedlinePlus Medical Encyclopedia [accessed on Apr 04, 2020]
Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."
Additional Materials (11)
Nasapharyngeal swab
Nasapharyngeal swab
Image by CDC and TheVisualMD
Throat Culture
Image by BruceBlaus
Pertussis Testing Video: Collecting a Nasopharyngeal Swab Clinical Specimen
Video by Centers for Disease Control and Prevention (CDC)/YouTube
NEJM Procedure: Collection of Nasopharyngeal Specimens with the Swab Technique
Video by NEJMvideo/YouTube
Conducting a nasopharyngeal swab test for COVID-19
Video by LAU Medical Center-Rizk Hospital/YouTube
How to Collect a Throat Swab Specimen
Video by PuritanUSA/YouTube
Pertussis Testing Video: Collecting a Nasopharyngeal Aspirate Clinical Specimen
Video by Centers for Disease Control and Prevention (CDC)/YouTube
How to do a Swab for COVID Testing
Video by Mount Sinai Health System/YouTube
Combination Nasal and Throat Swab Procedure
Video by COPANusa/YouTube
How to perform a throat swab on a patient
Video by Medscape/YouTube
Coronavirus COVID19 swab guidance
Video by Maudsley NHS/YouTube
Nasapharyngeal swab
CDC and TheVisualMD
Throat Culture
BruceBlaus
4:13
Pertussis Testing Video: Collecting a Nasopharyngeal Swab Clinical Specimen
Centers for Disease Control and Prevention (CDC)/YouTube
0:41
NEJM Procedure: Collection of Nasopharyngeal Specimens with the Swab Technique
NEJMvideo/YouTube
1:27
Conducting a nasopharyngeal swab test for COVID-19
LAU Medical Center-Rizk Hospital/YouTube
1:30
How to Collect a Throat Swab Specimen
PuritanUSA/YouTube
4:15
Pertussis Testing Video: Collecting a Nasopharyngeal Aspirate Clinical Specimen
Centers for Disease Control and Prevention (CDC)/YouTube
2:18
How to do a Swab for COVID Testing
Mount Sinai Health System/YouTube
1:42
Combination Nasal and Throat Swab Procedure
COPANusa/YouTube
0:44
How to perform a throat swab on a patient
Medscape/YouTube
3:33
Coronavirus COVID19 swab guidance
Maudsley NHS/YouTube
Respiratory Pathogens Panel
Respiratory Pathogens Panel
Also called: RP panel, Respiratory virus profile, RVP, Syndromic multiplex panel
A respiratory pathogens (RP) panel tests for different viruses and bacteria in the respiratory tract. It can enable faster, more accurate diagnoses of respiratory infections.
Respiratory Pathogens Panel
Also called: RP panel, Respiratory virus profile, RVP, Syndromic multiplex panel
A respiratory pathogens (RP) panel tests for different viruses and bacteria in the respiratory tract. It can enable faster, more accurate diagnoses of respiratory infections.
A respiratory pathogens (RP) panel checks for pathogens in the respiratory tract. A pathogen is a virus, bacteria, or other organism that causes an illness. Your respiratory tract is made up of parts of the body involved in breathing. This includes your lungs, nose, and throat.
There are many types of viruses and bacteria that can infect the respiratory tract. Symptoms are often similar, but treatment can be very different. So it's important to make the right diagnosis. Other viral and bacterial tests for respiratory infections are often limited to testing for one specific pathogen. Several samples may be needed. The process can be difficult and time consuming.
An RP panel only needs a single sample to run tests for a wide variety of viruses and bacteria. Results usually come in a few hours. Results from other types of respiratory tests can take a few days. Faster results may allow you to get started earlier on the right treatment.
A respiratory pathogens panel is used to help diagnose:
Viral infections, such as:
Flu
Common cold
Respiratory syncytial virus (RSV). This is a common and usually mild respiratory infection. But it can be dangerous to babies and the elderly.
Adenovirus infection. Adenoviruses cause many different types of infections. These include pneumonia and croup, an infection that causes hoarse, barking coughs.
Bacterial infections, such as:
Whooping cough
Bacterial pneumonia
You may need this test if you have symptoms of a respiratory infection and are at risk for complications. Most respiratory infections cause mild to moderate symptoms. But the infections can be serious or even life threatening to young children, the elderly, and people with weakened immune systems.
Symptoms of a respiratory infection include:
Coughing
Trouble breathing
Sore throat
Stuffy or runny nose
Fatigue
Loss of appetite
Fever
There are two ways a provider may take a sample for testing:
Nasopharyngeal swab:
You will tip your head back.
Your health care provider will insert a swab into your nostril until it reaches the upper part of your throat.
Your provider will rotate the swab and remove it.
Nasal aspirate:
Your provider will inject a saline solution into your nose, then remove the sample with gentle suction.
You don't need any special preparations for a respiratory pathogens panel.
The swab test may tickle your throat or cause you to cough. The nasal aspirate may be uncomfortable. These effects are temporary.
A negative result may mean your symptoms were caused by a pathogen not included in the panel of tests. It may also mean you have a condition not caused by a virus or bacteria.
A positive result means a specific pathogen was found. It tells you which type of infection you have. If more than one part of the panel was positive, it means you may be infected with more than one pathogen. This is known as a co-infection.
Based on your results, your provider will recommend treatment and/or order more tests. These may include a bacteria culture, viral blood tests, and a Gram stain. The tests may help confirm your diagnosis and guide treatment.
LabCorp Test Menu. 139250: Respiratory Virus Profile (RVP), PCR. [accessed on Nov 16, 2018]
Quest Diagnostics. Respiratory Virus PCR Panel I. [accessed on Nov 16, 2018]
Arup Consult. Respiratory Viruses. [accessed on Nov 16, 2018]
Adenovirus Test
Adenovirus Test
Adenoviruses are common viruses that can cause cold-like symptoms, sore throat, bronchitis, pneumonia, diarrhea, and pink eye (conjunctivitis). Adenovirus infections can be identified using antigen detection, polymerase chain reaction (PCR), virus isolation, and serology laboratory tests.
Adenovirus Test
Adenoviruses are common viruses that can cause cold-like symptoms, sore throat, bronchitis, pneumonia, diarrhea, and pink eye (conjunctivitis). Adenovirus infections can be identified using antigen detection, polymerase chain reaction (PCR), virus isolation, and serology laboratory tests.
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Use the slider below to see how your results affect your
health.
Your result is Negative.
A negative result does not rule out the presence of adenovirus; the sample may have presented low levels of the virus so that it was not identified as positive.
Related conditions
Adenovirus is a common virus that can affect your:
Eyes
Respiratory system (nose, mouth, throat, and lungs)
Gastrointestinal system (stomach and intestines)
It’s usually a mild virus that most people get during childhood. People with strong immune systems fight off the virus and have no long-term health problems. After your immune system fights it off, the virus may stay in your body even though it’s no longer causing symptoms.
People with weak immune systems have a higher risk of getting sick from the virus. Their bodies may have trouble fighting it off. That includes children and people taking medicine to weaken (suppress) the immune system after a transplant.
Adenovirus spreads easily through the air (coughing, sneezing) and by close contact (shaking hands).
Wash your hands with soap and water often throughout the day.
Cover your mouth and nose when coughing or sneezing.
Try not to touch your eyes, nose, or mouth.
Stay away from people who are sick.
If you start to feel sick — like you have a fever, diarrhea, or rash — tell your doctor. Your doctor will test for adenovirus by taking a blood sample and checking for the virus.
If you’ve had a transplant, your blood will be tested:
At least once a week during the first 100 days after your transplant
If you seem sick
While your immune system is weak, you’ll need regular tests. To be safe, you’ll keep getting tests even if they keep showing that you don’t have the virus. A weak immune system means you’re at high risk and could get adenovirus at any time.
If the test shows you have adenovirus, your doctor may give you a drug to help kill the virus. You’ll keep taking the drug until:
Your blood test shows a lower level of the virus.
Your blood test doesn’t show any virus.
Your immune system is back to normal.
https://cc.nih.gov/ccc/patient_education/pepubs/adenovirus.pdf [accessed on Nov 16, 2018]
Adenovirus | Clinical Overview | CDC [accessed on Nov 16, 2018]
Adenovirus | Clinical Diagnosis | CDC [accessed on Nov 16, 2018]
Adenovirus | ARUPConsult Lab Test Selection [accessed on Nov 16, 2018]
Molecular Diagnostics Adenovirus Tests & Products [accessed on Nov 16, 2018]
Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."
How to Treat a Stomach Flu or Virus | Stomach Problems
Video by Howcast/YouTube
Gastroenteritis Bacterial
Video by DrER.tv/YouTube
The HELP Video Guide To Gastroenteritis
Video by PatientEducationHELP/YouTube
Adenovirus structure
Adenovirus structure
Image by National Human Genome Research Institute
Electron cryomicroscopy
Cryo Electron Microscopy : The cryo EM facility specializes in visualizing biological complexes such as viruses, small organelles, and macromolecular biological complexes of 200 kDa or larger preserved in non-crystaline ice. The near native imaging conditions allows three dimensional reconstruction of the cellular machinary. Using state of the art computer controlled, automated microscopes, image reconstruction software, and visualization tools, sub-nanometer resolution structures of large biological complexes can be achieved.
Image by structbio.vanderbilt.edu
Adenovirus infection
Structure of adenovirus.
Image by Pico en el Ojo
Adenovirus Infections, Human
This transmission electron microscopic (TEM) image reveals some of the ultrastructural morphology exhibited by two adenovirus-2 virions. The sample had been pelleted, thereby, concentrating the viral particles prior to viewing under the microscope. Visible at this high magnification are the capsomeres, which in this case, were hexagonally-shaped, also known as a hexon, and which together comprised the outer covering of the adenovirus known as a capsid. These adenoviruses displayed an icosahedral symmetry, which means that the shape was characterized by 12 vertices, and 20 facets. Each virion was 70nm – 80nm, and exhibited no spikes.
Image by CDC/ Dr. John Hierholzer
Gene Therapy
Gene therapy is an experimental technique for treating disease by altering the patient's genetic material.
Image by National Human Genome Research Institute (NHGRI)
A simplified 3D-generated structure of the adenovirus
A simplified 3D-generated structure of the adenovirus
Image by Thomas Splettstoesser (www.scistyle.com)
Transmission electron micrograph of adenovirus
Transmission electron micrograph of adenovirus
Image by CDC/Dr. G. William Gary, Jr.
HeLa Cells with Adenovirus
A scanning electron micrograph of cultured HeLa cells originally derived many years ago from a woman's cancerous cervical tissue. A light micrograph (x130) of the same cells (inset) reveals rounded double cells in the center in the process of dividing. This HeLa cell (named after patient Henrietta Lacks) has been infected with adenovirus. After 4-1/2 hours the HeLa cell's surface becomes rough. The multiple surface blebs on this cell characteristic for a certain stage of cell division that both normal and cancer cells go through. Research with the SEM has established the extraordinarily responsive nature of cell surface form. This instrument records, in pictures, specific cell reactions to various changes in the cells environment and maps the distribution of surface binding sites for biologically important molecules such as hormone, antigens, and pharmacologic agents.
Image by Dr. Timothy Triche. National Cancer Institute / Unknown Photographer
Viral Evolution, Morphology, and Classification
Viruses can be either complex in shape or relatively simple. This figure shows three relatively complex virions: the bacteriophage T4, with its DNA-containing head group and tail fibers that attach to host cells; adenovirus, which uses spikes from its capsid to bind to host cells; and HIV, which uses glycoproteins embedded in its envelope to bind to host cells. Notice that HIV has proteins called matrix proteins, internal to the envelope, which help stabilize virion shape. (credit “bacteriophage, adenovirus”: modification of work by NCBI, NIH; credit “HIV retrovirus”: modification of work by NIAID, NIH)
Image by CNX Openstax (credit “bacteriophage, adenovirus”: modification of work by NCBI, NIH; credit “HIV retrovirus”: modification of work by NIAID, NIH)
Viral Evolution, Morphology, and Classification
Adenovirus (left) is depicted with a double-stranded DNA genome enclosed in an icosahedral capsid that is 90–100 nm across. The virus, shown clustered in the micrograph (right), is transmitted orally and causes a variety of illnesses in vertebrates, including human eye and respiratory infections. (credit “adenovirus”: modification of work by Dr. Richard Feldmann, National Cancer Institute; credit “micrograph”: modification of work by Dr. G. William Gary, Jr., CDC; scale-bar data from Matt Russell)
Image by CNX Openstax
Adenovirus virions
This digitally-colorized transmission electron microscopic (TEM) image revealed some of the ultrastructural details exhibited by a small cluster of adenovirus virions.
How to Treat a Stomach Flu or Virus | Stomach Problems
Howcast/YouTube
2:56
Gastroenteritis Bacterial
DrER.tv/YouTube
3:01
The HELP Video Guide To Gastroenteritis
PatientEducationHELP/YouTube
Adenovirus structure
National Human Genome Research Institute
Electron cryomicroscopy
structbio.vanderbilt.edu
Adenovirus infection
Pico en el Ojo
Adenovirus Infections, Human
CDC/ Dr. John Hierholzer
Gene Therapy
National Human Genome Research Institute (NHGRI)
A simplified 3D-generated structure of the adenovirus
Thomas Splettstoesser (www.scistyle.com)
Transmission electron micrograph of adenovirus
CDC/Dr. G. William Gary, Jr.
HeLa Cells with Adenovirus
Dr. Timothy Triche. National Cancer Institute / Unknown Photographer
Viral Evolution, Morphology, and Classification
CNX Openstax (credit “bacteriophage, adenovirus”: modification of work by NCBI, NIH; credit “HIV retrovirus”: modification of work by NIAID, NIH)
Viral Evolution, Morphology, and Classification
CNX Openstax
Adenovirus virions
CDC/ Dr. G. William Gary, Jr.
RSV Tests
RSV Tests
Also called: Respiratory Syncytial Virus (RSV) Tests
RSV is a respiratory infection that can be especially dangerous to babies and the elderly. RSV testing is used to diagnose the infection. Two types of tests are commonly used to diagnose RSV infections: rapid RSV antigen tests and molecular tests.
RSV Tests
Also called: Respiratory Syncytial Virus (RSV) Tests
RSV is a respiratory infection that can be especially dangerous to babies and the elderly. RSV testing is used to diagnose the infection. Two types of tests are commonly used to diagnose RSV infections: rapid RSV antigen tests and molecular tests.
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Use the slider below to see how your results affect your
health.
Your result is Negative.
A negative result means there is no RSV infection and the symptoms are likely caused by another type of virus.
Related conditions
RSV stands for respiratory syncytial virus. It is an infection that affects the respiratory tract. Your respiratory tract includes your lungs, nose, and throat. RSV testing checks a fluid sample from your nose to see if the RSV virus is causing symptoms of a respiratory infection.
RSV is very contagious, which means it spreads easily from person to person. It's also very common. Most children get RSV by the age of two. RSV usually causes mild symptoms that are like a cold. But the virus may lead to serious breathing problems, especially in certain groups of people, including:
Infants, especially those 6 months and younger
Older adults, especially those 65 years and older
People with heart or lung diseases
People with weakened immune systems
Two types of tests are commonly used to diagnose RSV infections:
Rapid RSV antigen tests are the most common test for RSV. They check a fluid sample from your nose for certain proteins from the RSV virus called antigens. RSV antigens trigger your immune system to attack the virus. Rapid antigen tests can provide results in an hour or less.
Molecular tests called RT-PCR (polymerase chain reaction) tests look for genetic material from the RSV virus in your sample. These tests can find smaller amounts of the virus than antigen tests. So, RT-PCR tests may be used for older children and adults who tend to have less of the virus in their noses than infants and younger children. Samples are usually sent to a lab for testing. In certain cases, your provider may order a molecular test called a respiratory pathogens panel. This test checks for RSV and other respiratory viruses and bacterial infections at the same time.
Other names: respiratory syncytial antibody test, RSV rapid detection
An RSV test is usually used to see if RSV is the cause of moderate to severe cold symptoms in infants, older adults, and people with weakened immune systems. People with mild symptoms may be tested as part of public health efforts to track the spread of the virus.
The test is usually done during the "RSV season," the time of year when RSV outbreaks are more common. In the United States, RSV season usually starts in mid-fall and ends in early spring, but the season may vary in different parts of the country.
Healthy adults and older children usually don't need RSV testing. Most RSV infections only cause mild symptoms such as a runny nose, sneezing, and headaches. But an infant, younger child, or an adult over age 65 may need an RSV test if they have symptoms of moderate or serious infection. These include:
Fever
Wheezing
Serious cough
Breathing faster than normal or trouble breathing
Blue skin color
In infants less than six months old, the only symptoms of RSV may be:
Acting cranky or irritable
Moving less than usual
Lack of appetite
Pauses in breathing
Tests to diagnose RSV are done on a sample of fluid from your nose. There are different ways to collect the sample:
Nasal aspirate or wash. This is the most common way to collect a sample for RSV testing. To do a nasal aspirate, a health care professional will insert a saline solution (salt water) into your nose and remove it with gentle suction.
Nasal swab test. A health care professional will use a special swab to take a sample from your nose.
RSV test samples should be taken during the first few days after symptoms begin. That's because the amount of the virus in your nose decreases over time, which may make test results less accurate.
At-home test kits are available to buy without a prescription. The test checks for RSV, flu, and COVID-19 using one sample. The kit includes a nasal swab to collect the sample to send to a lab for testing. Talk with your provider about using an at-home test.
Blood tests aren't usually used to diagnose RSV, but they can show if a recent illness was an RSV infection. So public health officials may use blood tests to measure the size of an RSV outbreak in the community.
You don't need any special preparations for an RSV test.
There is very little risk to RSV testing.
A nasal aspirate or wash may feel uncomfortable. These effects are temporary.
A swab test may cause a gagging feeling or brief discomfort when your nose is swabbed.
A negative result means that no signs of the RSV virus were found in your sample. They may mean that another illness is causing your symptoms.
But a negative test result does not rule out RSV. It's possible that there was not enough of the virus in the sample for the test to find it.
A positive result means that you likely have an RSV infection.
Infants, young children and older adults may need treatment in the hospital if they are having trouble breathing or have lost too much fluid and become dehydrated. Treatment may include oxygen and intravenous (IV) fluids. In the most serious cases, a breathing machine called a ventilator may be needed, but this is uncommon.
If you have RSV symptoms, but are otherwise in good health, your provider probably won't order RSV testing. Most healthy adults and children with RSV will get better in 1-2 weeks. Your provider may recommend over-the-counter medicines and drinking plenty of fluids to relieve your symptoms. Talk with your child's provider before giving your child any medicines.
Respiratory Syncytial Virus (RSV) Tests: MedlinePlus Medical Test [accessed on Mar 07, 2024]
Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."
Additional Materials (14)
Respiratory Syncytial Virus
Respiratory syncytial virus (RSV) causes infections of the lungs and respiratory tract. It is a common viral respiratory infection that tends to be seasonal, causing community epidemics in young children, older adults, and those whose immune systems are compromised. RSV enters your body through your eyes, nose or mouth. It spreads easily when infectious respiratory secretions, such as those from coughing or sneezing, are inhaled or passed to others through direct contact, such as shaking hands. Currently, there is no vaccine for RSV. A short-term drug therapy that can minimize lower respiratory tract symptoms after infection is given to some high-risk people.
Image by TheVisualMD
Human Respiratory Syncytial Virus (RSV)
Creative artwork featuring 3D renderings of respiratory syncytial virus (RSV)—a common contagious virus that infects the human respiratory tract—colorized in Halloween-appropriate colors (the viral envelope is magenta, G- glycoproteins are light purple, and F-glycoproteins are green). F-glycoproteins allow the virus to fuse with and infect human cells.
Image by NIAID
RSV disease (serious threat to children)
Video by ncccollegeny/YouTube
Infectious Diseases A-Z: What parents of babies need to know about bronchiolitis
Scanning electron micrograph of human respiratory syncytial virus (RSV) virions (colorized blue) that are labeled with anti-RSV F protein/gold antibodies (colorized yellow) shedding from the surface of human lung epithelial A549 cells. RSV is a common contagious virus that infects the human respiratory tract.
Image by NIAID
What Is Bronchitis?
Bronchitis : Figure A shows the location of the lungs and bronchial tubes in the body. Figure B is an enlarged, detailed view of a normal bronchial tube. Figure C is an enlarged, detailed view of a bronchial tube with bronchitis. The tube is inflamed and contains more mucus than usual.
Image by National Heart Lung and Blood Institute
X-ray of a child with RSV
An X-ray of a child with RSV showing the typical bilateral perihilar fullness of bronchiolitis.
Image by James Heilman, MD
Respiratory Syncytial Virus
This image depicts a photomicrograph of an unidentified tissue sample, that was been processed using the indirect immunofluorescent antibody (IFA) technique, and viewed under fluorescent lighting. Note the detection of what had been the respiratory syncytial virus (RSV), a negative-sense, enveloped RNA virus. The virion is variable in shape and size (120 - 300 nm), is unstable in the environment, surviving only a few hours on environmental surfaces, and is readily inactivated with soap and water and disinfectants.
Image by CDC/ Dr. H. Craig Lyerla
How Can Bronchitis Be Prevented?
Image by BruceBlaus
Bronchi Transport Air in the Respiratory System
Respiration is how the body absorbs oxygen from the air and eliminates the carbon dioxide produced by the body's cells. The respiratory system is chiefly composed of the nasal and oral cavities, larynx, pharynx, trachea, and lungs, along with the smaller bronchi and microscopic air sacs called alveoli within the lungs. Fetal lung tissue matures late in gestation and is filled with amniotic fluid until birth. A protein-lipid combination called surfactant plays a critical role in lung development. Surfactant maintains proper surface tension in the alveoli, keeping them from collapsing and making breathing possible. Researchers have discovered that nutrients such as vitamin D also play important roles in the healthy development of the infant's respiratory system.
Image by TheVisualMD
Babies Sitting Showing Respiratory Lymphatic Circulatory and Skeletal Systems
One of the most obvious ways that we notice the overall immune health of a baby is through the presence or absence of respiratory infections. Respiratory illness is the leading cause of hospitalization among young children. Lymph nodes and vessels are a direct component of the immune system. Lymph nodes are encapsulated bundles of lymph tissue found throughout the body especially in the neck, axillae, groin, and thoracic regions. Lymph tissue aids the immune system by collecting and breaking down toxins and other waste products of the body. Lymph vessels transport lymph, a clear fluid derived from intercellular spaces around the body, eventually back into the blood. An infant's circulatory system will face an olympian job over the course of the individual's lifetime; the heart will beat 2.5 billion times and pump millions of gallons of blood through the body's vast network of arteries and veins. An infant's heart doubles in size the first year of life. Nutrition plays a key role in the development and maintenance of a healthy circulatory system by providing building blocks such as iron needed for red blood cell production.
Image by TheVisualMD
Baby Sitting Showing Respiratory System
A baby's first breath is dramatic for all kinds of reasons, including physiological ones. A protein-lipid combination called surfactant plays a critical role in lung development. Researchers have discovered that nutrients such as vitamin D also play important roles in the healthy development of the infant's respiratory system. One of the most obvious ways that we notice the overall immune health of a baby is through the presence or absence of respiratory infections. Respiratory illness is the leading cause of hospitalization among young children. And when it is severe enough to require hospitalization, respiratory illness greatly increases the risk of childhood asthma.
Image by TheVisualMD
Healthy Cilia / Smoke-Damaged Cilia
Respiratory Cilia Damaged by Smoking
1) A close up view of healthy respiratory cilia, the hairlike structures that line the respiratory pathway. Healthy cilia move in a regular pattern to push foreign contaminants, bound in mucus, out toward the mouth and nose to be expelled from the body.
2) A close up view of damaged respiratory cilia, the hairlike structures that line the respiratory pathway. Unhealthy cilia are worn down and some are incapable of movement. They cannot beat in unison to push contaminants out of the respiratory system, as they do when healthy.
Interactive by TheVisualMD
Respiratory Syncytial Virus
TheVisualMD
Human Respiratory Syncytial Virus (RSV)
NIAID
1:39
RSV disease (serious threat to children)
ncccollegeny/YouTube
1:11
Infectious Diseases A-Z: What parents of babies need to know about bronchiolitis
Babies Sitting Showing Respiratory Lymphatic Circulatory and Skeletal Systems
TheVisualMD
Baby Sitting Showing Respiratory System
TheVisualMD
Respiratory Cilia Damaged by Smoking
TheVisualMD
Human Metapneumovirus Test
Human Metapneumovirus Test
Also called: HMPV
The human metapneumovirus (HMPV) is a recently (2001) discovered agent of viral respiratory infections. Clinical presentation ranges from the common cold to pneumonia. Co-infection with other respiratory viruses is common.
Human Metapneumovirus Test
Also called: HMPV
The human metapneumovirus (HMPV) is a recently (2001) discovered agent of viral respiratory infections. Clinical presentation ranges from the common cold to pneumonia. Co-infection with other respiratory viruses is common.
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Use the slider below to see how your results affect your
health.
Your result is Negative.
A negative result means you likely don't have a human metapneumovirus infection, and that some other virus is probably causing your symptoms. Your health care provider may order more tests before making a diagnosis.
Related conditions
Human metapneumovirus (HMPV) can cause upper and lower respiratory disease in people of all ages, especially among young children, older adults, and people with weakened immune systems. Discovered in 2001, HMPV is in the paramyxovirus family along with respiratory syncytial virus (RSV). Broader use of molecular diagnostic testing has increased identification and awareness of HMPV as an important cause of upper and lower respiratory infection.
Symptoms commonly associated with HMPV include cough, fever, nasal congestion, and shortness of breath. Clinical symptoms of HMPV infection may progress to bronchitis or pneumonia and are similar to other viruses that cause upper and lower respiratory infections. The estimated incubation period is 3 to 6 days, and the median duration of illness can vary depending upon severity but is similar to other respiratory infections caused by viruses.
Infection with HMPV can be confirmed usually by:
direct detection of viral genome by polymerase chain reaction assays, and
direct detection of viral antigens in respiratory secretions using immunofluorescence or enzyme immunoassay.
NREVSS | Human Metapneumovirus Clinical Features | CDC [accessed on Nov 16, 2018]
Metapneumovirus - hMPV | ARUPConsult Lab Test Selection [accessed on Nov 16, 2018]
Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."
Parainfluenza Tests
Parainfluenza Tests
Also called: Human parainfluenza virus test, HPIV test
Human parainfluenza viruses (HPIV) are among the most common causes of respiratory illness especially in young children. Parainfluenza tests diagnose four common viruses that cause respiratory illnesses, including croup and bronchitis.
Parainfluenza Tests
Also called: Human parainfluenza virus test, HPIV test
Human parainfluenza viruses (HPIV) are among the most common causes of respiratory illness especially in young children. Parainfluenza tests diagnose four common viruses that cause respiratory illnesses, including croup and bronchitis.
Parainfluenza viruses are a group of four types of viruses. They are a common cause of respiratory (breathing) illnesses. These illnesses can affect your, nose, throat, lungs, and bronchial tubes (the airways that carry air to your lungs). Parainfluenza tests check whether a parainfluenza virus is causing an illness. The tests usually use a sample of fluid from your nose or mucus from your lungs.
Parainfluenza viruses are also called human parainfluenza viruses (HPIVs). They aren't the same as flu (influenza) viruses. The flu is more common in winter. In the U.S., parainfluenza viruses are more common in the spring, summer, and fall.
Like the flu, parainfluenza spreads easily from person to person. It can spread through the air when a person with the infection coughs or sneezes. You can also get the flu by touching a surface that has the flu virus on it, and then touching your mouth, nose, or eyes.
Parainfluenza viruses commonly cause respiratory illness in babies and younger children, but anyone can get sick from these viruses. You can also have parainfluenza illnesses many times in your life. If you're healthy, you'll probably have mild symptoms that are much like a common cold, such a runny nose, fever, or cough. And you'll usually get better on your own.
Older adults and people of all ages who have weakened immune systems are more likely to develop more serious illness from parainfluenza infections. These illnesses include croup, bronchitis, and pneumonia.
The most common test for parainfluenza viruses is a molecular test, such as a PCR (polymerase chain reaction) tests. These tests can find very small amounts of genetic material from parainfluenza viruses in the fluid sample from your nose or lungs.
Other tests for parainfluenza virus are used less often than molecular tests. Rapid antigen tests are less accurate and must be done within a week after symptoms begin. Viral culture tests take much longer than other tests. And blood tests are mainly used for research.
Most healthy people who have symptoms of a respiratory illness do not need parainfluenza testing. That's because they usually get better on their own. But you may need this test if you have a high risk of getting seriously ill from a parainfluenza infection because you:
Have a condition that affects your immune system, such as:
Blood stem cell or bone marrow transplants
Organ transplantation
Blood cancers
HIV
Have a heart or lung disorder
Are in the hospital with community-acquired pneumonia (pneumonia that you catch during your usual daily life, not from spending time in a hospital or other health facility)
Are an older adult
For these people, treatment decisions depend on knowing whether they have a viral or bacterial infection. So, parainfluenza testing may be done as part of a respiratory pathogens panel. This is a group of tests that checks for several viruses and bacteria that cause respiratory illnesses. There is no cure for parainfluenza viruses, but bacterial infections may be treated with antibiotics.
You or your child may need a parainfluenza test if either of you have:
Symptoms of a respiratory illness.
And another condition that increases your risk of getting seriously sick from a parainfluenza illness.
Symptoms of parainfluenza and other respiratory illnesses may include:
Fever
Sore throat
Wheezing
A long-lasting cough that may sound like a barking in children (croup)
Shortness of breath
Too much mucus in the lungs or airways (congestion)
Rapid breathing
Tests to diagnose parainfluenza viruses are usually done on a sample of fluid from your nose or chest.
A sample from your nose may be used if you've had symptoms between 3 and 7 days. Most tests are done with this type of sample. The sample may be collected using one of these methods:
Nasal aspirate or wash. To do a nasal aspirate, a health care professional will insert a saline solution (salt water) into your nose and remove it with gentle suction.
Swab test. A health care professional will use a special swab to take a sample from either:
Deep in the back of your nose
An inch deep inside both of your nostrils and from your throat using a separate swab inserted through your mouth
A sample from your chest may be used at any time during your illness. The fluid may be collected with one of these methods:
Sputum test. Sputum is a thick mucus from the lungs. It is different from saliva (spit). To get a sample, you will be asked to cough up sputum into a special container.
Bronchoalveolar lavage (BAL). A BAL collects a sample of fluid from your lung. This type of sample is usually used only if you are very ill. A doctor will insert a narrow, flexible tube (a bronchoscope) down your throat and into your lung. A small amount of salt water will be injected through the tube into your lung and then suctioned out. Numbing medicine will be used in your mouth and throat. You may also have medicine to help you relax.
If you have a BAL, you may need to fast (not eat or drink) for several hours before the test. You should plan to have someone take you home because you may feel sleepy if you are given medicine to relax.
You don't need any special preparations for other parainfluenza tests.
There is very little risk to having a parainfluenza test:
A nasal aspirate or wash may feel uncomfortable. These effects are temporary.
Nasal and throat swabs may cause a brief gagging feeling.
A BAL may cause a sore throat for a few days. Serious problems are rare. They include bleeding in the airways, infection, or a partly collapsed lung.
A negative result means that no signs of parainfluenza viruses were found in your sample. Another illness is probably causing your symptoms. But a negative test result doesn't rule out a parainfluenza illness. It's possible that there was too little virus in your sample for the test to find.
A positive result means that you likely have a parainfluenza infection. But it's possible for a PCR test to show signs of a virus even though you don't have enough virus in your body to make you sick.
Talk with your provider about what your test results mean.
Parainfluenza Tests: MedlinePlus Medical Test [accessed on Sep 22, 2022]
Human Parainfluenza Viruses | Home | HPIVs | CDC [accessed on Nov 16, 2018]
Parainfluenza Virus 1, 2, 3, 4 | ARUPConsult Lab Test Selection [accessed on Nov 16, 2018]
Molecular Diagnostics Parainfluenza Virus Tests & Products [accessed on Nov 16, 2018]
Neutrophil Count
Neutrophil Count
Also called: Neutrophils (Complete Blood Count), Neutrophils, Neutropenia Test, Neutrophilia Test
This test measures the amount of neutrophils in a sample of your blood. Neutrophils are the most common type of white blood cell. They are your body's main defense against infection when bacteria, viruses, or other germs enter your body. An abnormal level of neutrophils circulating in the blood could indicate a number of health issues.
Neutrophil Count
Also called: Neutrophils (Complete Blood Count), Neutrophils, Neutropenia Test, Neutrophilia Test
This test measures the amount of neutrophils in a sample of your blood. Neutrophils are the most common type of white blood cell. They are your body's main defense against infection when bacteria, viruses, or other germs enter your body. An abnormal level of neutrophils circulating in the blood could indicate a number of health issues.
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Use the slider below to see how your results affect your
health.
%
40
60
Your result is Normal.
About 40 to 60 percent of all white blood cells are neutrophils.
Related conditions
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Use the slider below to see how your results affect your
health.
(10³)/μL
1.8
7.8
Your result is Normal.
About 40 to 60 percent of all white blood cells are neutrophils. A normal neutrophil count for adults usually is between 1,800 and 7,800 neutrophils per microliter of blood.
Related conditions
A neutrophil is a type of immune cell that is one of the first cell types to travel to the site of an infection. Neutrophils help fight infection by ingesting microorganisms and releasing enzymes that kill the microorganisms. A neutrophil is a type of white blood cell, a type of granulocyte, and a type of phagocyte.
Neutrophils are the most abundant white blood cells, accounting for about 40% to 60% of all white blood cells circulating in the blood. Neutrophils are historically defined as "soldiers of our innate immune system." They are the first line of cells recruited at the site of infection and attack, ingest, and digest invading microorganisms, including fungi and bacteria. Failure to carry out this role leads to immunodeficiency, which is mainly characterized by the presence of recurrent infections.
Normally, most of the neutrophils circulating in the bloodstream are in a mature form, with the nucleus of the cell being divided or segmented. Because of the segmented appearance of the nucleus, neutrophils are sometimes referred to as "segs." The nucleus of less mature neutrophils is not segmented, but has a band or rod-like shape. Therefore, less mature neutrophils are known as band-form neutrophils or "bands".
The number of neutrophils in your blood is measured as part of a blood differential test.
A blood differential test is often part of a general physical exam. Because the different types of white blood cell do different jobs, measuring them separately can give your health care provider important information about your health.
The test can also help diagnose a variety of medical conditions, such as:
Infections
Autoimmune diseases
Inflammatory diseases
Leukemia and other types of cancer
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
No special preparation is necessary.
There is very little risk to having a blood test. After the test, some people experience mild pain, dizziness, or bruising. These symptoms usually go away quickly.
The results can be expressed as a percentage (of the total number of all white blood cells) or as an absolute value.
An increased neutrophil number in your blood, a condition called neutrophilia or neutrophilic leukocytosis, is usually the result of:
Acute infections, primarily by bacteria, less frequently by viruses or fungi.
Tissue inflammation, such as in inflammatory bowel disease or rheumatoid arthritis.
Tissue death (necrosis), caused either by trauma, heart attack, burns, or major surgery.
Blood cancer (leukemia).
Pregnancy, temporary during the last trimester or labor.
Severe stress.
Strenuous physical exercise.
A low neutrophil count in your blood, a condition called neutropenia, may be a consequence of:
Chemotherapy during cancer treatment.
Overwhelming infection (sepsis).
Negative reaction to some drugs.
Aplastic anemia (a condition where the body stops producing enough new blood cells).
Myelodysplastic syndrome (the bone marrow produce poorly formed blood cells or cells that don't work properly).
A small percentage of band-form neutrophils is normal in the blood. However, an increased count of these cells (bandemia) is referred to as “left shift” and can be caused by acute infection (sepsis) or inflammation (acute appendicitis or cholecystitis).
Blood Differential: MedlinePlus Medical Test [accessed on Jan 22, 2024]
Blood differential test: MedlinePlus Medical Encyclopedia [accessed on Jan 22, 2024]
White Blood Cell (WBC) Differential - Testing.com. Aug 7, 2022 [accessed on Jan 22, 2024]
DALE.DAVID. Neutropenia - Blood Disorders - MSD Manual Consumer Version [accessed on Jan 22, 2024]
DALE.DAVID. Neutrophilic Leukocytosis - Blood Disorders - MSD Manual Consumer Version [accessed on Jan 22, 2024]
Patrick M. Zito. Neutropenia. StatPearls Publishing. Aug 25, 2022 [accessed on Jan 22, 2024]
Farah Zahra. Neutrophilia. StatPearls Publishing. Apr 27, 2023 [accessed on Jan 22, 2024]
Complete Blood count with Differential [accessed on Jan 22, 2024]
Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."
Additional Materials (20)
Neutrophil granulocyte
Neutrophil granulocytes (also known as neutrophils) : Neutrophils with a segmented nuclei surrounded byerythrocytes, the intra-cellular granules are visible in the cytoplasm
Neutrophil
Neutrophil function, relationship to disease, and location in the human body. Credit: NIAID
Image by NIAID
Klebsiella pneumoniae Bacteria
Produced by the National Institute of Allergy and Infectious Diseases (NIAID), this digitally colorized scanning electron microscopic (SEM) image, depicts a blue-colored, human white blood cell, (WBC) known specifically as a neutrophil, interacting with two pink-colored, rod shaped, multidrug-resistant (MDR), Klebsiella pneumoniae bacteria, which are known to cause severe hospital acquired, nosocomial infections.
Image by David Dorward; Ph.D.; National Institute of Allergy and Infectious Diseases (NIAID)
White Blood Cell and Red Blood Cell
Medical visualization of blood cells. Depicted are numerous red blood cells and a single white blood cell.
Image by TheVisualMD
Hematopoeisis Diagram
Many cells can result from one stem cell. Because division can occur at different stages of the cell's development, a single cell has the potential to become eight to 32 RBCs.
Image by TheVisualMD
Neutrophil
The most abundant type of white blood cells. They are normally found in the blood stream however during the acute phase of inflammation, neutraphils leave the vasculature and migrate toward the site of inflammation in a process called chemotaxis.
Image by TheVisualMD
Anthrax - How People Are Infected?
Neutrophil engulfing anthrax bacteria : Neutrophil (yellow) engulfing anthrax bacteria (orange), taken with a Leo 1550 scanning electron microscope. Scale bar is 5 micrometers.
Image by Volker Brinkmann
Splenic infarction
Blood smear from an adult female with a myelodysplastic syndrome related to radiotherapy and chemotherapy for Hodgkin disease. A hypogranular neutrophil with a pseudo-Pelger-Huet nucleus is shown. The red blood cells show marked poikilocytosis, in part related to post-splenectomy status. (Wright-Giemsa stain).
Image by The Armed Forces Institute of Pathology (AFIP)
Inflammation
Illustration of the Inflammatory Process
Image by OpenStax College
Bone structure
Anatomy of the bone. The bone is made up of compact bone, spongy bone, and bone marrow. Compact bone makes up the outer layer of the bone. Spongy bone is found mostly at the ends of bones and contains red marrow. Bone marrow is found in the center of most bones and has many blood vessels. There are two types of bone marrow: red and yellow. Red marrow contains blood stem cells that can become red blood cells, white blood cells, or platelets. Yellow marrow is made mostly of fat.
Image by Smart Servier website
Neutrophil
Image by BruceBlaus
Cell line plasma cells
Diagram showing the cell line plasma cells
Image by Cancer Research UK uploader
Neutrophils and How White Blood Cells Work
Video by TheCancer Immunity/YouTube
Extravasation of Neutrophils
Video by Katie Bergdale/YouTube
high white blood cell count Video
Video by itbestshop/YouTube
Learning to Decode Your Blood Test Results for Chronic Lymphocytic Leukemia (CLL)
Video by CLL Society/YouTube
Immune- Documentary - Part 4 - Neutrophils
Video by Rajesh kumar/YouTube
Neutrophils and Platelets: Why Are They Monitored So Closely?
Video by Patient Power - a Cancer Community/YouTube
Neutropenia - Mayo Clinic
Video by Mayo Clinic/YouTube
Neutropenia
Blood film with a striking absence of neutrophils, leaving only red blood cells and platelets
Image by Roberto J. Galindo
Neutrophil granulocyte
Neutrophil
NIAID
Klebsiella pneumoniae Bacteria
David Dorward; Ph.D.; National Institute of Allergy and Infectious Diseases (NIAID)
White Blood Cell and Red Blood Cell
TheVisualMD
Hematopoeisis Diagram
TheVisualMD
Neutrophil
TheVisualMD
Anthrax - How People Are Infected?
Volker Brinkmann
Splenic infarction
The Armed Forces Institute of Pathology (AFIP)
Inflammation
OpenStax College
Bone structure
Smart Servier website
Neutrophil
BruceBlaus
Cell line plasma cells
Cancer Research UK uploader
2:15
Neutrophils and How White Blood Cells Work
TheCancer Immunity/YouTube
2:27
Extravasation of Neutrophils
Katie Bergdale/YouTube
8:22
high white blood cell count Video
itbestshop/YouTube
1:17:17
Learning to Decode Your Blood Test Results for Chronic Lymphocytic Leukemia (CLL)
CLL Society/YouTube
1:58
Immune- Documentary - Part 4 - Neutrophils
Rajesh kumar/YouTube
3:37
Neutrophils and Platelets: Why Are They Monitored So Closely?
Patient Power - a Cancer Community/YouTube
6:37
Neutropenia - Mayo Clinic
Mayo Clinic/YouTube
Neutropenia
Roberto J. Galindo
Treatment
Flu, Influenza, Cold, Virus, Sick
Image by stevepb/Pixabay
Flu, Influenza, Cold, Virus, Sick
Image by stevepb/Pixabay
Treatment of Flu
If you get sick with flu, antiviral drugs may be a treatment option.
Check with your doctor promptly if you are at higher risk of serious flu complications and you get flu symptoms. People at higher risk of flu complications include young children, adults 65 years of age and older, pregnant people, and people with certain medical conditions, such as asthma, diabetes and heart disease.
When used for treatment, antiviral drugs can lessen symptoms and shorten the time you are sick by 1 or 2 days. They also can prevent serious flu complications, like pneumonia. For people at higher risk of serious flu complications, treatment with antiviral drugs can mean the difference between milder or more serious illness possibly resulting in a hospital stay. CDC recommends prompt treatment for people who have flu or suspected flu and who are at higher risk of serious flu complications.
Source: Centers for Disease Control and Prevention (CDC)
What can you do to protect yourself and your loved ones? If you have not received a flu vaccine, it is not too late! Flu vaccines reduce the risk of flu illness and potentially serious flu complications that can result in hospitalization and death. Flu activity usually peaks between December and February, although activity can last as late as May.
Document by Centers for Disease Control and Prevention (CDC)
The Flu and You | Does antiviral medication work against the current strain of the flu?
The Flu and You | Does antiviral medication work against the current strain of the flu?
Johns Hopkins Medicine/YouTube
Antiviral Drugs
The interaction of the anti-influenza drug Relenza™, buried in the active site pocket of influenza virus neuraminidase protein.
Image by CSIRO
The interaction of the anti-influenza drug Relenza™, buried in the active site pocket of influenza virus neuraminidase protein.
The interaction of the anti-influenza drug Relenza™, buried in the active site pocket of influenza virus neuraminidase protein.
Image by CSIRO
Flu Treatment: What You Need to Know
Antiviral Drugs
Most people with flu have mild illness and do not need medical care or antiviral drugs. If you get sick with flu symptoms, in most cases, you should stay home and avoid contact with other people except to get medical care.
If, however, you have symptoms of flu and are in a higher risk group, are very sick or worried about your illness, contact your health care provider. CDC recommends prompt treatment for people who have flu or suspected flu who are at higher risk of serious flu complications, such as people with asthma, diabetes, or heart disease.
Antiviral drugs can help treat flu illness:
Antiviral drugs are different from antibiotics. Flu antivirals are prescription medicines (pills, liquid, intravenous solution, or an inhaled powder) and are not available over the counter.
Antiviral drugs can make illness milder and shorten the time you are sick. They also can prevent serious flu complications, like pneumonia, when treatment is started early.
It’s very important that antiviral drugs be used early to treat people who are very sick with flu (for example, people who are in the hospital) and people who are sick with flu and have a greater chance of getting serious flu complications, either because of their age or because they have a higher risk medical condition. Other people also may be treated with antiviral drugs by their doctor this season. Most otherwise-healthy people who get flu, however, do not need to be treated with antiviral drugs.
Studies show that flu antiviral drugs work best for treatments when they are started within 2 days of getting sick. However, starting them later can still be helpful, especially if the sick person has a higher-risk health condition or is very sick from flu (for example, hospitalized patients). Follow your doctor’s instructions for taking these drugs.
If you get sick:
Take Antivirals Drugs, if prescribed by a health care provider
Take everyday precautions to protect others while sick
While sick, limit contact with others as much as possible to keep from infecting them.
Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
Clean and disinfect surfaces and objects that may be contaminated with germs like flu.
Stay home until you are better
If you are sick with flu-like illness, CDC recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. Your fever should be gone without the use of fever-reducing medicine.
See Other Important Information for People Who are Sick.
In the context of the COVID-19 pandemic, local governments or public health departments may recommend additional precautions be taken in your community. Follow those instructions.
Treatment Questions
Can flu be treated? Yes. There are prescription medications called “antiviral drugs” that can be used to treat flu illness.
What are flu antiviral drugs? Flu antiviral drugs are prescription medicines (pills, liquid, an inhaled powder, or an intravenous solution) that fight against flu in your respiratory tract. Antiviral drugs are not sold over the counter. You can only get them if you have a prescription from your doctor or health care provider. Antiviral drugs are different from antibiotics, which fight against bacterial infections.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (3)
Antiviral Drugs: Seasonal Flu
Video by Centers for Disease Control and Prevention (CDC)/YouTube
Video by MedCram - Medical Lectures Explained CLEARLY/YouTube
The targets of anti-influenza agents that are currently licensed or under clinically investigation.
The targets of anti-influenza agents that are currently licensed or under clinically investigation. Before attachment of the influenza virus particle (IVP) to the host cell, specific neutralizing monoclonal antibodies (mAbs) against conserved domains in HA can prevent viral infection. Enzymatic destruction of the receptor determinant can further prevent IVP-binding to the target cells. After binding of the IVP to host cell sialic-acid receptors the viral life-cycle is continued by receptor-mediated endocytosis, HA-mediated fusion of the viral membrane with vesicular membrane, vRNP uncoating and release into the cytosol. The viral genome is then replicated/transcribed in the nucleus. After the viral mRNA has been translated into proteins some undergo post-translational processing in the cytosol or support genome replication in the nucleus. Newly formed vRNPs are exported from the nucleus and finally progeny virions are assembled and released by budding from the infected cell to infect new cells. These different processes are potential targets for the currently licensed antiviral drugs and others, which are in clinical trials including CR6261, CR8020, MEDI8852, MHAA4549A, VIS-410 (neutralizing Abs); DAS181 (sialidase); Umifenovir (fusion inhibitor); adamantanes (M2 channel blockers); Favipiravir and Ribavirin (RdRp inhibitors); VX-787 (PB2 cap-binding inhibitor); S-033188 (PA endonuclease inhibitor); AVI-7100 (inhibits M1/M2 mRNA-splicing); Nitazoxanide (HA maturation inhibitor); and Oseltamivir, Peramivir, Zanamivir, and Laninamivir (Neuraminidase inhibitors). In addition to its NF-κB inhibition effect, LASAG antagonizes the nuclear export of viral genomes and thereby blocks the assembly and release of mature influenza virus.
Image by Ahmed Mostafa, Elsayed M. Abdelwhab, Thomas C. Mettenleiter, and Stephan Pleschka
1:18
Antiviral Drugs: Seasonal Flu
Centers for Disease Control and Prevention (CDC)/YouTube
MedCram - Medical Lectures Explained CLEARLY/YouTube
The targets of anti-influenza agents that are currently licensed or under clinically investigation.
Ahmed Mostafa, Elsayed M. Abdelwhab, Thomas C. Mettenleiter, and Stephan Pleschka
Natural Products
Cough mixture ingredients
Image by sunny mama/Wikimedia
Cough mixture ingredients
I made this photo for a tutorial blog post on how to make your own cough mixture: hallosunny.blogspot.nl/2014/11/diy-zelf-hoestdrank-maken....
You can use it, but please link back to the original blog post.
Image by sunny mama/Wikimedia
5 Tips: What Does the Science Say About Natural Products for the Flu and Colds?
It’s that time of year again—cold and flu season.
Each year, approximately 5 to 20 percent of Americans come down with the flu. Although most recover without incident, flu-related complications typically lead to at least 200,000 hospitalizations and between 12,000 and 60,000 deaths each year. Colds generally do not cause serious complications, but they are among the leading reasons for visiting a doctor and for missing school or work.
Some people try natural products such as herbs or vitamins and minerals to prevent or treat these illnesses. But do they really work? What does the science say?
Vaccination is the best protection against getting the flu. Starting in 2010, the Federal Government’s Centers for Disease Control and Prevention has recommended annual flu vaccination for all people aged 6 months and older.
There is currently no strong scientific evidence that any natural product is useful against the flu.
Zinc taken orally (by mouth) may help to treat colds, but it can cause side effects and interact with medicines. Zinc is available in two forms—oral zinc (e.g., lozenges, tablets, syrup) and intranasal zinc (e.g., swabs and gels). A 2015 analysis of clinical trials found that oral zinc helps to reduce the length of colds when taken within 24 hours after symptoms start. Intranasal zinc has been linked to a severe side effect (irreversible loss of the sense of smell) and should not be used.
A note about safety:Oral zinc can cause nausea and other gastrointestinal symptoms. Long-term use of zinc, especially in high doses, can cause problems such as copper deficiency. Zinc may interact with drugs, including antibiotics and penicillamine (a drug used to treat rheumatoid arthritis).
Vitamin C does not prevent colds and only slightly reduces their length and severity. A 2013 review of scientific literature found that taking vitamin C regularly did not reduce the likelihood of getting a cold but was linked to small improvements in cold symptoms. In studies in which people took vitamin C only after they got a cold, vitamin C did not improve their symptoms.
A note about safety:Vitamin C is generally considered safe; however, high doses can cause digestive disturbances such as diarrhea and nausea.
Echinacea has not been proven to help prevent or treat colds. Echinacea is an herbal supplement that some people use to treat or prevent colds. Echinacea products vary widely, containing different species, parts, and preparations of the echinacea plant. Reviews of research have found limited evidence that some echinacea preparations may be useful for treating colds in adults, while other preparations did not seem to be helpful. In addition, echinacea has not been shown to reduce the number of colds that adults catch. Only a small amount of research on echinacea has been done in children, and the results of that research are inconsistent.
A note about safety: Few side effects have been reported in clinical trials of echinacea; however, some people may have allergic reactions. In one large clinical trial in children, those who took echinacea had an increased risk of developing rashes.
The evidence that probiotic supplements may help to prevent colds is weak, and little is known about their long-term safety. Probiotics are a type of “good bacteria,” similar to the microorganisms found in the body, and may be beneficial to health. Probiotics are available as dietary supplements and yogurts, as well as other products such as suppositories and creams. Although a 2015 analysis of research indicated that probiotics might help to prevent upper respiratory tract infections, such as the common cold, the evidence is weak and the results have limitations.
A note about safety:Little is known about the effects of taking probiotics for long periods of time. Most people may be able to use probiotics without experiencing any side effects—or with only mild gastrointestinal side effects such as gas —but there have been some case reports of serious side effects. Probiotics should not be used by people with serious underlying health problems except with close monitoring by a health care provider.
Source: National Center for Complementary and Integrative Health (NCCIH)
Additional Materials (4)
No, Vitamin C won't cure your cold
Video by Vox/YouTube
Can zinc really prevent COVID-19?
Video by Demystifying Medicine/YouTube
Can Vitamin C and Zinc Help Cure Colds?
Video by SciShow/YouTube
Importance of Zinc for the Immune System
Video by Dr. Eric Berg DC/YouTube
4:08
No, Vitamin C won't cure your cold
Vox/YouTube
5:29
Can zinc really prevent COVID-19?
Demystifying Medicine/YouTube
4:27
Can Vitamin C and Zinc Help Cure Colds?
SciShow/YouTube
3:43
Importance of Zinc for the Immune System
Dr. Eric Berg DC/YouTube
Prevention
Woman gets bandage after receiving a flu shot
Image by Petty Officer 2nd Class Jonathan Word; Camp Lemonnier, Djibouti
Woman gets bandage after receiving a flu shot
U.S. Navy Lt. Amanda Brock, a critical care nurse assigned to the Michaud Expeditionary Medical Facility at Camp Lemonnier, Djibouti (CLDJ), receives a bandage after being administered a flu vaccine. CLDJ serves as an expeditionary base for U.S. military forces providing support to ships, aircraft and personnel that ensure security throughout Europe, Africa and Southwest Asia. The base enables maritime and combat operations in the Horn of Africa while fostering positive U.S.-Africa relations. (U.S. Navy photo by Mass Communication Specialist 2nd Class Jonathan Word)
Image by Petty Officer 2nd Class Jonathan Word; Camp Lemonnier, Djibouti
How to Prevent Flu
Take time to get a flu vaccine.
CDC recommends a yearly flu vaccine as the first and most important step in protecting against flu viruses.
Flu vaccines help to reduce the burden of flu illnesses, hospitalizations and deaths on the health care system each year.
This season, all flu vaccines will be designed to protect against the four flu viruses that research indicates will be most common.
Everyone 6 months and older should get an annual flu vaccine, ideally by the end of October.
Vaccination of people at higher risk of developing serious flu complications is especially important to decrease their risk of severe flu illness.
People at higher risk of serious flu complications include young children, pregnant people, people with certain chronic health conditions like asthma, diabetes or heart and lung disease, and people 65 years and older.
Vaccination also is important for health care workers, and other people who live with or care for people at higher risk to keep from spreading flu to them. This is especially true for people who work in long-term care facilities, which are home to many of the people most vulnerable to flu.
Children younger than 6 months are at higher risk of serious flu illness but are too young to be vaccinated. People who care for infants should be vaccinated instead.
Take everyday preventive actions to stop the spread of germs.
Take everyday preventive actions that are recommended to reduce the spread of flu.
Avoid close contact with people who are sick.
If you are sick, limit contact with others as much as possible to keep from infecting them.
Cover coughs and sneezes.
Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
Avoid touching your eyes, nose, and mouth. Germs spread this way.
Clean and disinfect surfaces and objects that may be contaminated with viruses that cause flu.
For flu, CDC recommends that people stay home for at least 24 hours after their fever is gone except to get medical care or other necessities. Fever should be gone without the need to use a fever-reducing medicine. Note that the stay-at-home guidance for COVID-19 may be different.
Take flu antiviral drugs if your doctor prescribes them.
If you are sick with flu, antiviral drugs can be used to treat your illness.
Antiviral drugs are different from antibiotics. They are prescription medicines (pills, liquid or an inhaled powder) and are not available over-the-counter.
Flu antiviral drugs can make flu illness milder and shorten the time you are sick. They may also prevent serious flu complications. For people with higher risk factors, treatment with an antiviral drug can mean the difference between having a milder illness versus a very serious illness that could result in a hospital stay.
Studies show that flu antiviral drugs work best for treatment when they are started within 2 days of getting sick, but starting them later can still be helpful, especially if the sick person has a higher risk factor or is very sick from flu.
If you are at higher risk from flu and get flu symptoms, call your health care provider early so you can be treated with flu antivirals if needed. Follow your doctor’s instructions for taking this drug.
Flu symptoms include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. Some people also may have vomiting and diarrhea. People may be infected with flu and have respiratory symptoms without a fever.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (8)
How The Flu Shot Works (And Why You Should Get It)
Video by Seeker/YouTube
The Flu: A Guide for Parents - Factsheets
The Flu: A Guide for Parents - Factsheets
Document by CDC
Take Three Actions to Fight Flu Infographic
Take Three Actions to Fight Flu Infographic
Document by CDC
No Time For Flu :30 | Flu Vaccination | Ad Council
Video by Ad Council/YouTube
How can I prevent the spread of the flu?
Video by U.S. Department of Health and Human Services/YouTube
Misconceptions about Flu and the Flu Vaccine
Video by Centers for Disease Control and Prevention (CDC)/YouTube
Can the Flu shot cause the flu?
Video by Demystifying Medicine/YouTube
How the flu vaccine may help prevent COVID-19 infection
Video by Good Morning America/YouTube
3:35
How The Flu Shot Works (And Why You Should Get It)
Seeker/YouTube
The Flu: A Guide for Parents - Factsheets
CDC
Take Three Actions to Fight Flu Infographic
CDC
0:38
No Time For Flu :30 | Flu Vaccination | Ad Council
Ad Council/YouTube
0:29
How can I prevent the spread of the flu?
U.S. Department of Health and Human Services/YouTube
10:27
Misconceptions about Flu and the Flu Vaccine
Centers for Disease Control and Prevention (CDC)/YouTube
6:25
Can the Flu shot cause the flu?
Demystifying Medicine/YouTube
2:33
How the flu vaccine may help prevent COVID-19 infection
Good Morning America/YouTube
Caring for Someone Sick
Boy with Fever having his temperature taken
Image by Victoria Borodinova
Boy with Fever having his temperature taken
Boy with Fever having his temperature taken
Image by Victoria Borodinova
Influenza (Flu) - Caring for Someone Sick
Steps to Take if You Get the Flu
If you get very sick, are pregnant, or are 65 years or older, or are otherwise at high risk of flu-related complications, call your doctor. You might need antiviral drugs to treat flu.
Stay at home and rest.
Avoid close contact with well people in your house so you won’t make them sick.
Drink plenty of water and other clear liquids to prevent fluid loss (dehydration).
When caring for people who have the flu:
Avoid being face to face with the sick person. If possible, it is best to spend the least amount of time in close contact with a sick person.
When holding sick children, place their chin on your shoulder so they will not cough in your face.
Wash your hands often and right way.
If soap and water are not available, use an alcohol-based hand rub.
Make sure to wash your hands after touching the sick person. Wash after handling their tissues or laundry.
Get immediate medical care if the sick person experiences:
In children
Fast breathing or trouble breathing
Bluish lips or face
Ribs pulling in with each breath
Chest pain
Severe muscle pain (child refuses to walk)
Dehydration (no urine for 8 hours, dry mouth, no tears when crying)
Not alert or interacting when awake
Seizures
Fever above 104°F
In children less than 12 weeks, any fever
Fever or cough that improve but then return or worsen
Worsening of chronic medical conditions
In adults
Difficulty breathing or shortness of breath
Persistent pain or pressure in the chest or abdomen
Persistent dizziness, confusion, inability to arouse
Seizures
Not urinating
Severe muscle pain
Severe weakness or unsteadiness
Fever or cough that improve but then return or worsen
Worsening of chronic medical conditions
These lists are not all inclusive. Please consult your medical provider for any other symptom that is severe or concerning.
Source: Centers for Disease Control and Prevention (CDC)
Additional Materials (1)
How to Care for Someone with Influenza
Video by Stanford Health Care/YouTube
2:13
How to Care for Someone with Influenza
Stanford Health Care/YouTube
Glossary of Terms
Glossary of Influenza (Flu) Terms
Please click on the alphabetically ordered sections below to expand content and see glossary terms along with their associated definitions.
A
Term
Definition
Acute respiratory illness (ARI)
Acute respiratory illness (ARI) is disease that typically involves the airways within the nose and throat (i.e., the upper respiratory tract) and that may or may not include fever (measured by a thermometer) or feverishness (i.e., self-reported sense of fever). ARI is generally defined as the presence of two or more signs or symptoms such as fever, cough, runny nose or nasal congestion, or sore throat). ARI is a more sensitive (broader) way than influenza-like illness (ILI) to describe illness consistent with influenza (flu) because fever or feverishness is not required.
Adjuvant
A vaccine adjuvant is a substance that is added to a vaccine to increase and improve the body’s immune response to the vaccine antigen(s). Antigens are the components of the flu vaccine that prompt your body to have an immune response. Vaccine adjuvants can allow flu vaccines to be produced using less antigen. Therefore, use of adjuvants can allow vaccine manufacturers to produce more doses of vaccine with less antigen.
Antigen
A protein on the surface of an influenza (flu) virus that can stimulate an immune response. Antigen is the component of the flu vaccine that prompts your body’s immune response. The immune response to vaccination results in the development of protective antibodies against the viruses used to make the vaccine.
Antiviral chemoprophylaxis
Antiviral chemoprophylaxis is the use of influenza (flu) antiviral drugs to prevent flu illness. Antiviral chemoprophylaxis is often used in response to flu outbreaks in nursing homes or other types of facilities that care for residents at high risk of flu complications, so as to prevent spread of disease. It is also used as a precautionary measure to prevent illness in people who have been exposed to animals infected with or environments contaminated by novel (i.e., new in humans) influenza A viruses, such as the viruses that cause bird flu or swine flu.
Asian HPAI H5N1 influenza virus
Asian HPAI H5N1 influenza viruses are avian influenza A viruses that originate from Asia and that cause severe illness and death in poultry (this means the viruses are “highly pathogenic” and these viruses are called “highly pathogenic avian influenza” or “HPAI” for short). These viruses were first detected in 1996 in geese in China. Asian HPAI H5N1 virus infection in humans was first detected in 1997 during poultry outbreaks in Hong Kong and has since been detected in poultry and wild birds in more than 60 countries in Africa, Asia, Europe, and the Middle East since 2003. HPAI H5N1 is regularly found (i.e., “endemic”) in poultry in six countries: Bangladesh, China, Egypt, India, Indonesia, and Vietnam. Asian HPAI H5N1 viruses have also infected other kinds of animals (e.g., dogs, cats, pigs, tigers, leopards, and stone martens). Asian HPAI H5N1 viruses are different from the HPAI H5N1, H5N2, and H5N8 viruses that have been detected in U.S. wild birds and poultry since December 2014.
Attenuated virus vaccine
An attenuated virus vaccine (such as the nasal spray flu vaccine, a.k.a. the “live attenuated influenza vaccine”) is a vaccine that consists of live virus that has been weakened through chemical or physical processes to produce an immune response without causing disease in the vaccinated person. The United States currently licenses attenuated vaccines for influenza, measles, mumps, rubella, polio, yellow fever and varicella (i.e., chicken pox).
Avian influenza A virus
Avian influenza A viruses (i.e., bird flu viruses) primarily infect birds. These viruses occur naturally among wild aquatic birds worldwide and can infect domestic poultry (such as chickens, ducks and turkeys) and other bird and animal species. Avian influenza A viruses are classified as low pathogenic or highly pathogenic based on molecular characteristics of the virus and the virus’ ability to cause disease and mortality in chickens in a laboratory setting. For more information, see the definitions for “highly pathogenic avian influenza” and “low pathogenic avian influenza“. Wild aquatic birds can be infected with avian influenza A viruses in their intestines and respiratory tract, but usually do not get sick. However, avian influenza A viruses are very contagious among birds and some of these viruses – particularly highly pathogenic avian influenza viruses – can sicken and even kill certain domesticated birds. In the past, some avian influenza A viruses (such as H5N1 and H7N9) have infected people, but human infections are rare. Since they do not typically spread among people and most people do not have antibodies against such viruses, avian influenza A viruses are also considered to be novel influenza A viruses.
C
Term
Definition
Candidate vaccine virus
A candidate vaccine virus is an influenza (flu) virus that has been prepared by CDC or its public health partners for use by vaccine manufacturers, if needed, to mass produce a flu vaccine. CDC collaborates in the preparation of candidate vaccine viruses that are provided to vaccine manufacturers prior to every flu season. In addition, as part of its pandemic influenza preparedness responsibilities, CDC produces candidate vaccine viruses against new (novel) influenza A viruses with pandemic potential. These candidate vaccine viruses can be used in case of a public health emergency to produce a pandemic flu vaccine.
Case under investigation (see also suspected case)
A patient who meets illness criteria for influenza (flu) but laboratory tests for influenza virus infection have not been performed. A case under investigation (CUI) will have an exposure history that will prompt a public health investigation. For example a CUI for avian influenza A(H7N9) virus infection could have illness compatible with flu and recent travel to a country where avian influenza A(H7N9) virus is circulating in birds. Suspected cases include but are not limited to CUI.
Close contact
A close contact is someone who has come within about 6 feet (2 meters) of a confirmed case or case under investigation (CUI) while the case was ill (beginning one day prior to symptom onset and continuing until resolution of illness). This can happen when health care personnel provide care for a confirmed or suspected case, family members of a confirmed or suspected case, people who lived with or stayed overnight with a confirmed or suspected case, and others who have had similar close or direct contact in a community or workplace environment.
Close proximity
Close proximity is generally thought to involve coming within about 6 feet (2 meters) of an infected person, infected animal or contaminated surface, but not touching or handling that person, animal or surface.
Confirmed influenza case
A patient who tests positive for influenza virus (flu) infection by an approved laboratory test.
Conjunctivitis
Conjunctivitis is the medical term for inflammation of the eyelids or the covering over the eye, typically caused by infection or chemical exposure. Some influenza (flu) viruses, such as some avian flu A (bird flu) viruses, can cause conjunctivitis in people.
D
Term
Definition
Direct contact
Direct contact means handling or touching. For example, direct contact with a bird may include activities such as de-feathering, butchering, or other activities which require touching.
E
Term
Definition
Emergency use authorization (EUA)
An emergency use authorization (EUA) in the United States is a legal means for the Food and Drug Administration (FDA) to allow for the use of drugs or provide new indications for previously approved drugs during a declared emergency.
Epidemic influenza
In general, a flu epidemic occurs when flu activity in an area (e.g., a city, a country, or another region) is higher than normal. In the United States, a flu epidemic occurs when flu activity is higher than a CDC-defined “baseline” value. The baseline may be the level of flu activity during months when flu viruses are not widely circulating spreading in people (usually from mid-May to September in the United States). For flu, there is a seasonal epidemic almost every year in the United States usually between October and mid-May. CDC and the medical community refer to this as the flu season. The season is marked by elevated flu activity across the nation. During the flu season, the level and timing of flu activity in specific states or counties might be different than in the country overall. Epidemics of influenza are not uncommon and can occur at any time—this is in contrast to pandemic influenza, which is quite rare.
H
Term
Definition
Hemagglutinin (HA)
Hemagglutinin (HA) is a surface protein found on influenza (flu) viruses. HA plays an important role in infection by allowing a flu virus to enter a healthy cell. HA is also an antigen. Antigens are molecular structures on the surface of viruses that are recognized by the immune system and are capable of triggering an immune response (i.e., the creation of antibodies). These antibodies protect the host from re-infection with the same influenza virus in the future. Therefore, HA is the active component (antigen) of inactivated flu vaccines. Most seasonal flu vaccines are designed to target the HA of the flu viruses that research suggests will be most common during the flu season.
Highly-pathogenic avian influenza (HPAI)
Avian influenza A viruses are classified into the following two categories: low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (HPAI) viruses. The categories refer to molecular characteristics of a bird flu virus and the virus’ ability to cause disease and mortality in chickens in a laboratory setting. HPAI viruses are highly contagious among birds and can be deadly to them, especially domestic poultry. Though relatively rare, sporadic human infections with HPAI H5 and HPAI H7 viruses have occurred and caused serious illness and death.
HPAI H5 viruses
This term is used to refer to highly-pathogenic avian influenza (HPAI) A (H5) viruses. Examples of HPAI H5 viruses include HPAI H5N1, HPAI H5N2, HPAI H5N6, HPAI H5N8 and HPAI H5N9.
I
Term
Definition
Inactivated vaccine
Inactivated vaccine refers to vaccine that contains inactivated or “dead” virus. The flu shot is an inactivated virus vaccine. Inactivated virus vaccines cannot cause infection in a vaccinated person.
Influenza-like illness (ILI)
ILI is defined as fever (temperature of 100 °F or greater) and cough and/or sore throat. It is used for flu surveillance worldwide.
L
Term
Definition
Long-term care facility (LTCF)
A health care facility, such as a nursing home, a skilled nursing facility, or an assisted living facility that provides medical and personal care to people who are unable to manage independently in the community. Influenza outbreaks occur at LTCFs every year, and LTCF residents are considered to be at high risk for developing flu-related complications.
Low pathogenic avian influenza (LPAI)
Avian influenza A viruses are classified into the following two categories: low pathogenic avian influenza (LPAI) A viruses and highly pathogenic avian influenza (HPAI) A viruses. The categories refer to molecular characteristics of a bird flu virus and the virus’ ability to cause disease and mortality in chickens in a laboratory setting. HPAI A viruses can cause very severe disease in birds; however, infection of poultry with LPAI viruses may cause no disease or mild illness (such as ruffled feathers and a drop in egg production) and may not be detected. Though relatively rare, sporadic human infections with LPAI viruses have occurred and have ranged in severity from mild illness to serious illness that can result in death.
N
Term
Definition
Neuraminidase (NA)
Neuraminidase (NA) is a surface protein found on influenza (flu) viruses. NA plays an important role in infection by allowing a flu virus to exit an infected cell in order to spread infection to other healthy cells. NA is also an antigen. The neuraminidase inhibitor class of antiviral drugs, which includes oseltamivir, zanamivir and peramivir work by targeting and inhibiting the function of the NA of an influenza virus.
Non-U.S. HPAI H5N1 virus
A highly pathogenic bird flu virus of the H5 subtype that has not been found in animals or people in the United States. For more information, see the definition for “highly pathogenic avian influenza” (HPAI).
Novel influenza A virus
A novel influenza (flu) A virus is an influenza A virus that has caused human infection and is different from current seasonal influenza A viruses spreading among people. Novel influenza A viruses can be viruses that originate in animals that gain the ability to infect and spread among humans or human viruses that change significantly so as to be different from current human seasonal influenza A viruses.
O
Term
Definition
Oseltamivir
Oseltamivir is an influenza (flu) antiviral drug that is approved for use in the United States. Antiviral drugs are prescription medications that can be used to treat (or prevent – see “antiviral chemoprophylaxis”) flu illness. Oseltamivir is available as a generic version or under the trade name Tamiflu® and given orally. It is a neuraminidase (NA) inhibitor that targets and inhibits the NA surface proteins of an influenza virus. For more information, see What you should know about flu antiviral drugs.
P
Term
Definition
Pandemic influenza
An influenza pandemic occurs when a novel influenza A virus spreads from person to person around the world and affects a very large number of people. A novel flu A virus might cause a flu pandemic if the novel virus can spread efficiently from person to person (instead of just from animals to people or from one person to another, but then no further). Another condition for a pandemic to occur is that most people will not have immunity to the new virus. People can have some immunity to novel or pandemic flu A viruses that are similar to flu A viruses they’ve been infected by in the past. If a new flu A virus is very different from earlier flu A viruses, it may be more likely to cause a pandemic. Influenza B viruses do not cause influenza pandemics.
Peramivir
Peramivir is an influenza (flu) antiviral drug that is approved for use in adults in the United States. It is an intravenous (IV) medication. Antiviral drugs are prescription medications that can be used to treat (or prevent – see “antiviral chemoprophylaxis”) flu illness. Peramivir is commercially available under the trade name Rapivab®. It is a neuraminidase (NA) inhibitor class antiviral drug that targets and inhibits the NA surface proteins of an influenza virus. For more information, see What you should know about flu antiviral drugs.
Person-to-person transmission
Person-to-person transmission is also called human-to-human transmission. This refers to the ability of an influenza (flu) virus to spread from one person to another (instead of from an animal to a person, for example). Seasonal influenza viruses spread easily from person to person, most commonly through large or small droplets containing influenza virus that are expelled when a sick person is coughing or sneezing. Most novel influenza A viruses do not spread easily.
Potential to cause severe disease
Some new influenza A viruses have not caused disease in humans, but are related to other viruses that have caused severe disease in people. An example of this is the HPAI A(H5N2) virus that caused outbreaks in birds in the U.S. beginning in December 2014, but has not yet been documented to infect people. CDC considers this HPAI A (H5N2) virus to have the potential to cause severe disease in people, since it is genetically related to the Asian HPAI A(H5N1) and A(H5N6) viruses that have caused severe and fatal disease in people.
Probable case
A patient who meets illness criteria for influenza (flu) but does not yet have laboratory confirmation of influenza virus infection. Probable cases are usually thought to be more likely to have a disease than cases under investigation. This can be because they have some laboratory evidence that suggests flu virus infection, but not enough evidence to confirm it.
R
Term
Definition
Reassortment
Reassortment refers to a process in which two or more influenza (flu) viruses infect a single host and exchange genetic material. This can result in the emergence of a novel (i.e., new) influenza A virus. Many of the past pandemics were caused by influenza A viruses from animals that gained the ability to infect and spread among humans by swapping genetic information with human influenza A viruses through the process of reassortment.
Respiratory specimen
A sample of respiratory secretions, such as a nose or throat swab that can be tested for influenza virus infection. Respiratory specimens are usually needed for laboratory testing to determine if a case under investigation for influenza is a confirmed case.
S
Term
Definition
Seasonal influenza virus
Seasonal influenza viruses are influenza A and B viruses that spread and cause illness in people during the time of year known as the “flu season.” Seasonal influenza viruses cause annual U.S. influenza epidemics during fall, winter, and spring, and circulate among people worldwide. Seasonal influenza A and B viruses are continually undergoing evolution in unpredictable ways.
Severe acute respiratory infection (SARI)
SARI is an acute respiratory infection (see ARI and ILI) that results in severe clinical illness, typically requiring hospitalization and/or resulting in death.
Suspected case (see case under investigation)
A patient who meets illness criteria for influenza but has not had laboratory testing for influenza virus infection. Suspected cases are now referred to as cases under investigation.
V
Term
Definition
Variant influenza virus
Influenza (flu) viruses that are known to circulate in pigs are called “swine influenza viruses” when isolated from pigs, but are called “variant viruses” when isolated from humans. Variant viruses are designated with the letter “v” (e.g., influenza A H3N2v). Note that “variant” is not used to describe influenza viruses from animals other than pigs. Variant influenza viruses are a subset of novel influenza A viruses.
Z
Term
Definition
Zanamivir
Zanamivir is an influenza (flu) antiviral drug that is approved for use in the United States. The approved form of zanamivir is available as an orally inhaled powder, which is commercially available under the trade name Relenza®. An intravenous form of zanamivir is available for compassionate use. Antiviral drugs are prescription medications that can be used to treat (or prevent – see “antiviral chemoprophylaxis”) flu illness. Zanamivir is a neuraminidase (NA) inhibitor class antiviral drug that targets and inhibits the NA surface proteins of an influenza virus. For more information, see What you should know about flu antiviral drugs.
Source: Centers for Disease Control and Prevention (CDC)
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Flu
The flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. The flu virus spreads mainly by tiny droplets made when people with flu cough, sneeze, or talk. Learn about the symptoms of flu as well as its diagnosis and treatment.