Noroviruses are a group of related viruses. Infection with these viruses causes an illness called gastroenteritis, an inflammation of the stomach and intestines. It can spread from person to person, or through contaminated food or water. You can also get it if you touch a contaminated surface. Norovirus can be serious, especially for young children and older adults.

The most common symptoms of norovirus infection are

• Diarrhea
• Nausea and vomiting
• Stomach pain

Other symptoms may include fever, headache or body aches.

Treatment includes bed rest and lots of liquids to prevent dehydration. There is no specific medicine to treat norovirus infections.

Proper hand washing and safe food preparation may help prevent infections.

About Norovirus

Norovirus is a very contagious virus that causes vomiting and diarrhea. Anyone can get infected and sick with norovirus. You can get norovirus from:

• Having direct contact with an infected person
• Consuming contaminated food or water
• Touching contaminated surfaces then putting your unwashed hands in your mouth

Norovirus Symptoms

The most common symptoms are:

• Diarrhea
• Vomiting
• Nausea
• Stomach pain

Prevent Norovirus

Protect yourself and others from norovirus:

• Wash your hands often
• Rinse fruits and vegetables
• Cook shellfish thoroughly
• Stay home when sick and for two days after symptoms stop
• Avoid preparing food for others when sick and for two days after symptoms stop

Trends and Outbreaks

• Outbreaks are common
• The virus spreads very easily and quickly
• Norovirus spreads:
  • From infected people to others
  • Through contaminated foods and surfaces
• Outbreaks can happen anytime, but they occur most often from November to April.

Stomach bug or norovirus?

You may hear norovirus illness be called “food poisoning”, “stomach flu”, or “stomach bug.” Noroviruses are the leading cause of foodborne illness. But, other germs and chemicals can also cause foodborne illness.

Norovirus illness is not related to the flu, which is caused by influenza virus.

Norovirus is a very contagious virus that causes vomiting and diarrhea. People of all ages can get infected and sick with norovirus. You can get it from having close contact with an infected person, consuming contaminated food or water, or by touching contaminated surfaces and then putting your fingers in your mouth. There’s no vaccine to prevent infection and no drug to treat it. Wash your hands often and follow some simple prevention tips to stay healthy.

Key Facts

• Norovirus causes about 20 million illnesses, 70,000 hospitalizations, and 800 deaths each year in the United States.
• Most people get norovirus from having close contact with an infected person or by eating contaminated food.
• Norovirus is the leading cause of foodborne illness in the United States.
• Symptoms of norovirus illness begin suddenly and usually include vomiting, diarrhea, nausea, and stomach pain.
• Infected people are contagious when they have symptoms but also spread it a few days before and after they have symptoms.

Practice Proper Hand Washing

Wash your hands with soap and water for at least 20 seconds. If soap and water are not readily available, you can use an alcohol-based hand sanitizer that contains at least 60% alcohol. You can tell if the sanitizer contains at least 60% alcohol by looking at the product label.

Protect Yourself from Norovirus

You can protect yourself and others from norovirus by following some simple tips: wash your hands often with soap and water for at least 20 seconds; cook shellfish to 140 degrees Fahrenheit or higher; don't prepare food or care for others when you're sick; rinse fruits and vegetables thoroughly; and, after vomiting or having diarrhea, immediately clean and disinfect surfaces and wash soiled laundry.

Avoid Dehydration

You may get dehydrated if you are not able to drink enough liquids to replace the fluids lost from throwing up or having diarrhea many times a day. The best way to prevent dehydration is to drink plenty of liquids.

Prevention Tips

• Wash your hands carefully and often with soap and water for at least 20 seconds. Alcohol-based hand sanitizers can be used in addition to hand washing, but they should not be a substitute for washing with soap and water.
• When preparing food, carefully rinse fruits and vegetables and thoroughly cook shellfish, such as oysters.
• Do not prepare food or provide care for others when you are sick with norovirus and for at least 3 days after you feel better.
• Immediately clean and sanitize surfaces that have been contaminated with diarrhea or vomit. Use disposable gloves to wipe up vomit or diarrhea with paper towels. Next, use a bleach cleaner on the surface, then clean the surface again with hot water and soap.

Norovirus spreads very easily and quickly in different ways.

You can get norovirus by accidentally getting tiny particles of poop or vomit from an infected person in your mouth.

This can happen if you

• eat food or drink liquids that are contaminated with norovirus,
• touch surfaces or objects contaminated with norovirus then put your fingers in your mouth, or
• have direct contact with someone who is infected with norovirus, such as by caring for them or sharing food or eating utensils with them.

If you get norovirus illness, you can shed billions of norovirus particles that you can’t see without a microscope. Only a few norovirus particles can make other people sick. You are most contagious

• when you have symptoms of norovirus illness, especially vomiting, and
• during the first few days after you recover from norovirus illness.

However, studies have shown that you can still spread norovirus for two weeks or more after you feel better.

Norovirus spreads through contaminated food

Norovirus can easily contaminate food and water because it only takes a very small amount of virus particles to make you sick. Food and water can get contaminated with norovirus in many ways, including when:

• An infected person touches food with their bare hands that have poop or vomit particles on them
• Food is placed on a counter or surface that has poop or vomit particles on it
• Tiny drops of vomit from an infected person spray through the air and land on the food
• The food is grown or harvested with contaminated water, such as oysters harvested from contaminated water, or fruit and vegetables irrigated with contaminated water in the field

Norovirus spreads through contaminated water

Recreational or drinking water can get contaminated with norovirus and make you sick or contaminate your food. This can happen:

• At the source such as when a septic tank leaks into a well
• When an infected person vomits or poops in the water
• When water isn’t treated properly, such as not enough chlorine

For more information on healthy water and how water can get contaminated, visit www.cdc.gov/healthywater/.

Norovirus spreads through sick people and contaminated surfaces

Surfaces can get contaminated with norovirus in many ways, including when:

• An infected person touches the surface with their bare hands that have feces or vomit particles on them
• An infected person vomits or has diarrhea that splatters onto surfaces
• Food, water, or objects that are contaminated with norovirus are placed on surfaces
• Tiny particles of vomit spray through the air and land on surfaces or enter a person’s mouth, then he or she swallows it

Do you think you have the stomach flu or a stomach bug?

It’s probably norovirus, a common virus that is not related to the flu. Norovirus is the most common cause of vomiting and diarrhea, and foodborne illness.

The most common symptoms of norovirus are:

• diarrhea
• vomiting
• nausea
• stomach pain

Other symptoms include:

• fever
• headache
• body aches

Norovirus causes inflammation of the stomach or intestines. This is called acute gastroenteritis.

A person usually develops symptoms 12 to 48 hours after being exposed to norovirus. Most people with norovirus illness get better within 1 to 3 days.

If you have norovirus illness, you can feel extremely ill, and vomit or have diarrhea many times a day. This can lead to dehydration, especially in young children, older adults, and people with other illnesses.

Symptoms of dehydration include:

• decrease in urination
• dry mouth and throat
• feeling dizzy when standing up

Children who are dehydrated may cry with few or no tears and be unusually sleepy or fussy.

There is no specific medicine to treat people with norovirus illness.

If you have norovirus illness, you should drink plenty of liquids to replace fluid lost from vomiting and diarrhea. This will help prevent dehydration.

Dehydration can lead to serious problems. Severe dehydration may require hospitalization for treatment with fluids given through your vein (intravenous or IV fluids).

Watch for signs of dehydration in children who have norovirus illness. Children who are dehydrated may cry with few or no tears and be unusually sleepy or fussy.

If you think you or someone you are caring for is severely dehydrated, call the doctor.

Antibiotic drugs will not help because they fight bacteria, not viruses.

Prevent Dehydration

Drink plenty of liquids to replace fluids that are lost from vomiting and diarrhea. Sports drinks and other drinks without caffeine or alcohol can help with mild dehydration. But, these drinks may not replace important nutrients and minerals. Oral rehydration fluids that you can get over the counter are most helpful for mild dehydration.

You can help protect yourself and others from norovirus by washing your hands thoroughly with soap and water and following other simple prevention tips.

Practice proper hand hygiene

Wash your hands thoroughly with soap and water

• especially after using the toilet or changing diapers,
• always before eating, preparing, or handling food, and
• before giving yourself or someone else medicine.

Norovirus can be found in your vomit or feces (poop) even before you start feeling sick. The virus can also stay in your feces for two weeks or more after you feel better. It is important to continue washing your hands often during this time.

You can use hand sanitizers in addition to hand washing, but you should not use hand sanitizer as a substitute for washing your hands with warm water and soap. Handwashing is always best.

Hand sanitizers aren’t as effective as washing hands with water and soap at removing norovirus particles.

Handle and prepare food safely

Carefully wash fruits and vegetables before preparing and eating them. Cook oysters and other shellfish thoroughly before eating them.

Be aware that noroviruses are relatively resistant to heat. They can survive temperatures as high as 145°F. Quick steaming processes that are often used for cooking shellfish may not heat foods sufficiently to kill noroviruses.

Food that might be contaminated with norovirus should be thrown out.

Keep sick infants and children out of areas where food is being handled and prepared.

When you are sick, do not prepare food or care for others

You should not prepare food for others or provide healthcare while you are sick and for at least two days after symptoms stop. This also applies to sick workers in restaurants, schools, daycares, long-term care facilities, and other places where they may expose people to norovirus.

Clean and disinfect surfaces

After someone vomits or has diarrhea, always thoroughly clean and disinfect the entire area immediately. Put on rubber or disposable gloves and wipe the entire area with paper towels, then disinfect the area using a bleach-based household cleaner as directed on the product label. Leave the bleach disinfectant on the affected area for at least five minutes, then clean the entire area again with soap and hot water. Finish by cleaning soiled laundry, taking out the trash, and washing your hands.

To help make sure that food is safe from norovirus, routinely clean and sanitize kitchen utensils, counters, and surfaces before preparing food.

You should use a chlorine bleach solution with a concentration of 1,000 to 5,000 ppm (5 to 25 tablespoons of household bleach [5% to 8%] per gallon of water) or other disinfectant registered as effective against norovirus by the Environmental Protection Agency (EPA).

Wash laundry thoroughly

Immediately remove and wash clothes or linens that may be contaminated with vomit or feces.

You should:

• handle soiled items carefully without agitating (shaking) them,
• wear rubber or disposable gloves while handling soiled items and wash your hands after, and
• wash the items with detergent (cleaning agent) and hot water at the maximum available cycle length and then machine dry them at the highest heat setting.

Have you ever experienced severe diarrhea or vomiting? If you have, it’s likely you had norovirus. If you haven’t, chances are you will sometime in your life. Norovirus is a very contagious virus that anyone can get from contaminated food or surfaces, or from an infected person. It is the most common cause of diarrhea and vomiting (also known as gastroenteritis) and is often referred to as food poisoning or stomach flu. In the United States, a person is likely to get norovirus about 5 times during their life.

Norovirus has always caused a considerable portion of gastroenteritis among all age groups. However, improved diagnostic testing and gains in the prevention of other gastroenteritis viruses, like rotavirus, are beginning to unmask the full impact of norovirus

For most people, norovirus causes diarrhea and vomiting which lasts a few days but, the symptoms can be serious for some people, especially young children and older adults. Each year in the United States, norovirus causes 19 to 21 million illnesses and contributes to 56,000 to 71,000 hospitalizations and 570 to 800 deaths.

Additionally, norovirus is increasingly being recognized as a major cause of diarrheal disease around the globe, accounting for nearly 20% of all diarrheal cases. In developing countries, it is associated with approximately 50,000 to 100,000 child deaths every year. Because it is so infectious, hand washing and improvements in sanitation and hygiene can only go so far in preventing people from getting infected and sick with norovirus.

This is why efforts to develop a vaccine are so important and why in February 2015 the Bill and Melinda Gates Foundation, CDC Foundation, and CDC brought together norovirus experts from around the world to discuss how to make the norovirus vaccine a reality. Participants were from 17 countries on 6 continents and included representatives from academia, industry, government, and private charitable foundations.

Important questions remain regarding how humans develop immunity to norovirus, how long immunity lasts, and whether immunity to one norovirus strain protects against infection from other strains. There are also relevant questions as to how a norovirus vaccine would be used to prevent the most disease and protect those at highest risk for severe illness. These are all critical questions for a vaccine, and this meeting was a step toward finding answers to these questions and making a norovirus vaccine a reality.

Noroviruses are a group of viruses that cause gastroenteritis [gas-trō-en-ter-ī-tis] in people. Gastroenteritis is an inflammation of the lining of the stomach and intestines, causing an acute onset of severe vomiting and diarrhea. Norovirus illness is usually brief in people who are otherwise healthy. Young children, the elderly, and people with other medical illnesses are most at risk for more severe or prolonged infection. Like all viral infections, noroviruses are not affected by treatment with antibiotics. Norovirus infections spread very rapidly. Healthcare facilities and other institutional settings (e.g., daycare centers, schools, etc.) are particularly at-risk for outbreaks because of increased person-to-person contact.

Symptoms of Norovirus

The symptoms of norovirus illness usually include nausea, vomiting, diarrhea, and some stomach cramping. Sometimes people also have a low-grade fever, chills, headache, muscle aches, and tiredness. People may suddenly feel very sick and vomit frequently or have several episodes of diarrhea, but most people get better within 1 or 2 days and they have no long-term health effects related to their illness. Diarrhea is more common in children and vomiting is more common in adults.

In some cases, people are unable to drink enough liquids to replace the liquids they lost because of frequent vomiting and diarrhea. This is called dehydration—the loss of a great deal of water from their body. Symptoms of dehydration include decreased urination, dry mouth and throat, and dizziness when standing up. In these cases, patients may be hospitalized and often given fluids through a tube placed in a vein.

Transmission of Norovirus

Noroviruses are found in the feces and vomit of infected people. This virus is very contagious and can spread rapidly throughout healthcare facilities. People can become infected with the virus in several ways:

• Having direct contact with another person who is infected (a healthcare worker, visitor, or another patient)
• Eating food or drinking liquids that are contaminated with norovirus
• Touching surfaces or objects contaminated with norovirus, and then touching your mouth or other food items

Prevention of Norovirus

In a healthcare facility, patients with suspected norovirus may be placed in private rooms or share rooms with other patients with the same infection. Additional prevention measures in healthcare facilities can decrease the chance of coming in contact with noroviruses:

• Follow hand-hygiene guidelines, and carefully washing of hands with soap and water after contact with patients with norovirus infection
• Use gowns and gloves when in contact with, or caring for patients who are symptomatic with norovirus
• Routinely clean and disinfect high touch patient surfaces and equipment with an Environmental Protection Agency-approved product with a label claim for norovirus
• Remove and wash contaminated clothing or linens
• Healthcare workers who have symptoms consistent with norovirus should be excluded from work