Lyme disease is the most common vector-borne disease in the United States. Lyme disease is caused by the bacterium Borrelia burgdorferi and rarely, Borrelia mayonii. It is transmitted to humans through the bite of infected blacklegged ticks. Typical symptoms include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system. Lyme disease is diagnosed based on symptoms, physical findings (e.g., rash), and the possibility of exposure to infected ticks.  Laboratory testing is helpful if used correctly and performed with validated methods. Most cases of Lyme disease can be treated successfully with a few weeks of antibiotics.

Steps to prevent Lyme disease include using insect repellent, removing ticks promptly, applying pesticides, and reducing tick habitat. The ticks that transmit Lyme disease can occasionally transmit other tickborne diseases as well.

Lyme disease is an infectious disease caused by Borrelia burgdorferi bacteria. The bacteria are transferred to humans by tick bite, specifically by blacklegged ticks (commonly known as deer ticks). The condition is named for the location in which it was first described, the town of Lyme, Connecticut.

If not treated with antibiotics, Lyme disease follows three stages: early localized, early disseminated, and late disseminated infection. A small percentage of individuals have symptoms that persist months or years after treatment, which is called post-treatment Lyme disease syndrome.

A characteristic feature of Lyme disease, and the key feature of early localized infection, is a slowly expanding red rash on the skin (called erythema migrans) at the site of the tick bite; the rash is often bull's-eye shaped. Flu-like symptoms and enlarged lymph nodes (lymphadenopathy) are also early signs of infection. Most people who are treated at this stage never develop further symptoms.

The early disseminated stage of Lyme disease occurs as the bacteria is carried throughout the body in the bloodstream. This stage occurs a few weeks after the tick bite. Signs and symptoms can include additional rashes on other parts of the body, flu-like symptoms, and lymphadenopathy. Some affected individuals develop neurologic problems (referred to as neuroborreliosis), such as paralyzed muscles in the face (facial palsy); pain, numbness, or weakness in the hands or feet; difficulty concentrating; or memory problems. Rarely, the heart is affected (Lyme carditis), causing a sensation of fluttering or pounding in the chest (palpitations) or an irregular heartbeat.

The late disseminated stage of Lyme disease can occur months to years after the tick bite. The most common feature of this stage, Lyme arthritis, is characterized by episodes of joint pain and swelling, usually affecting the knees. In rare cases, the late disseminated stage also involves neurological problems.

Individuals with post-treatment Lyme disease syndrome report ongoing exhaustion (fatigue), muscle and joint achiness, headache, or difficulty concentrating even after treatment with antibiotics, when there is no evidence of the bacteria in the body. Very rarely, individuals have joint pain and swelling for months or years after successful antibiotic treatment. This complication is called antibiotic-refractory Lyme arthritis.

What is Borrelia mayonii?

Borrelia mayonii are a type of bacteria recently found in North America that can cause Lyme disease. These bacteria are different from the three types of bacteria that cause most cases of Lyme disease worldwide.

• Borrelia burgdorferi (North America, Europe)
• B. afzelii (Europe, Asia)
• B. garinii (Europe, Asia)

B. mayonii is the only species besides B. burgdorferi shown to cause Lyme disease in North America.

How was it discovered?

In 2013, scientists at the Mayo Clinic noticed an unusual result while testing blood from patients who were thought to have Lyme disease. Cooperation between Mayo Clinic, state public health agencies, and CDC confirmed that a new type of bacteria that infects people had been found in blacklegged ticks.

Where does B. mayonii occur?

Current evidence suggests that within the United States, B. mayonii is only found in the Upper Midwest.

Has B. mayonii been found in ticks?

Yes, but not as often as B. burgdorferi. B. mayonii has been found in blacklegged ticks collected in northwestern Wisconsin and Minnesota. The blacklegged tick can also transmit B. burgdorferi (the bacteria that causes almost all Lyme disease infections in the United States), and the germs that cause anaplasmosis, babesiosis, and Powassan virus disease.

What type of illness does B. mayonii cause?

Based on limited information, illness caused by B. mayonii appears similar to that caused by B. burgdorferi, but with a few differences. Like B. burgdorferi, B. mayonii causes fever, headache, rash, and neck pain in the days after infection and can cause arthritis after a few weeks of illness. Unlike B. burgdorferi, B. mayonii can also cause nausea and vomiting; large, widespread rashes; and a higher concentration of bacteria in the blood.

What tests are used to diagnose B. mayonii?

Your healthcare provider may order a blood test to look for infection. Limited available information suggests that patients with B. mayonii infection develop antibodies that are similar to those of patients infected with B. burgdorferi. Therefore, Lyme disease serologic testing may help in diagnosing patients with B. mayonii. In some cases, B. mayonii bacteria may also be seen on a blood smear. Infection with B. mayonii can be specifically identified by Lyme disease molecular tests at Mayo Clinic. Lyme disease, including infection with B. mayonii, can be diagnosed without testing when patients have signs and symptoms consistent with Lyme disease and a history of possible exposure to blacklegged ticks.

How is B. mayonii treated?

Physicians have successfully treated patients infected with B. mayonii with a 2- to- 4-week course of doxycycline. Other antibiotics that are often used to successfully treat Lyme disease can also be used.

Why are we just discovering this now?

It is possible that the bacteria recently emerged or that the bacteria have been present in the area for a long time but hadn’t been discovered. Mayo Clinic tested roughly 100,000 patient samples in the same way for over a decade but only recently detected B. mayonii.

I live in the northeastern United States where Lyme disease is common. Should I be worried about B. mayonii?

At this time, there is no evidence that B. mayonii is found outside of the Upper Midwest. However, you should continue to take precautions against tick bites as Lyme disease, anaplasmosis, and babesiosis are common in much of the Northeast.

What more do researchers need to know?

CDC, Mayo Clinic, and the Minnesota Department of Health continue to test blood samples from patients suspected of tickborne illness, like Lyme disease, to learn more about tickborne bacteria that may cause human illness.

In addition, biologists continue to collect and test ticks throughout the United States to determine the range of the ticks that are infected with these bacteria.

How can I avoid this disease?

For more information, see Preventing Tick Bites.

What is Lyme disease?

Lyme disease is a bacterial infection you get from the bite of an infected tick. At first, Lyme disease usually causes symptoms such as a rash, fever, headache, and fatigue. But if it is not treated early, the infection can spread to your joints, heart, and nervous system. Prompt treatment can help you recover quickly.

What causes Lyme disease?

Lyme disease is caused by bacteria. In the United States, this is usually a bacterium called Borrelia burgdorferi. It spreads to humans through the bite of an infected tick. The ticks that spread it are blacklegged ticks (or deer ticks). They are usually found in the

• Northeast
• Mid-Atlantic
• Upper Midwest
• Pacific coast, especially northern California

These ticks can attach to any part your body. But they are often found in hard-to-see areas such as your groin, armpits, and scalp. Usually the tick must be attached to you for 36 to 48 hours or more to spread the bacterium to you.

Who is at risk for Lyme disease?

Anyone can get a tick bite. But people who spend lots of time outdoors in wooded, grassy areas are at a higher risk. This includes campers, hikers, and people who work in gardens and parks.

Most tick bites happen in the summer months when ticks are most active and people spend more time outdoors. But you can get bitten in the warmer months of early fall, or even late winter if temperatures are unusually high. And if there is a mild winter, ticks may come out earlier than usual.

What are the symptoms of Lyme disease?

Early symptoms of Lyme disease start between 3 to 30 days after an infected tick bites you. The symptoms can include

• A red rash called erythema migrans (EM). Most people with Lyme disease get this rash. It gets bigger over several days and may feel warm. It is usually not painful or itchy. As it starts to get better, parts of it may fade. Sometimes this makes the rash look like a "bull's-eye."
• Fever
• Chills
• Headache
• Fatigue
• Muscle and joint aches
• Swollen lymph nodes

If the infection is not treated, it can spread to your joints, heart, and nervous system. The symptoms may include

• Severe headaches and neck stiffness
• Additional EM rashes on other areas of your body
• Facial palsy, which is a weakness in your facial muscles. It can cause drooping on one or both sides of your face.
• Arthritis with severe joint pain and swelling, especially in your knees and other large joints
• Pain that comes and goes in your tendons, muscles, joints, and bones
• Heart palpitations, which are feelings that your heart is skipping a beat, fluttering, pounding, or beating too hard or too fast
• An irregular heart beat (Lyme carditis)
• Episodes of dizziness or shortness of breath
• Inflammation of the brain and spinal cord
• Nerve pain
• Shooting pains, numbness, or tingling in the hands or feet

How is Lyme disease diagnosed?

To make a diagnosis, your health care provider will consider

• Your symptoms
• How likely it is that you were exposed to infected blacklegged ticks
• The possibility that other illnesses may cause similar symptoms
• Results of any lab tests

Most Lyme disease tests check for antibodies made by the body in response to infection. These antibodies can take several weeks to develop. If you are tested right away, it may not show that you have Lyme disease, even if you have it. So you may need to have another test later.

What are the treatments for Lyme disease?

Lyme disease is treated with antibiotics. The earlier you are treated, the better; it gives you the best chance of fully recovering quickly.

After treatment, some patients may still have pain, fatigue, or difficulty thinking that lasts more than 6 months. This is called post-treatment Lyme disease syndrome (PTLDS). Researchers don't know why some people have PTLDS. There is no proven treatment for PTLDS; long-term antibiotics have not been shown to help. However, there are ways to help with the symptoms of PTLDS. If you have been treated for Lyme disease and still feel unwell, contact your health care provider about how to manage your symptoms. Most people do get better with time. But it can take several months before you feel all better.

Can Lyme disease be prevented?

To prevent Lyme disease, you should lower your risk of getting a tick bite:

• Avoid areas where ticks live, such as grassy, brushy, or wooded areas. If you are hiking, walk in the center of the trail to avoid brush and grass.
• Use an insect repellent with DEET
• Treat your clothing and gear with a repellant containing 0.5% permethrin
• Wear light-colored protective clothing, so you can easily see any ticks that get on you
• Wear a long-sleeve shirt and long pants. Also tuck your shirt into your pants and your pant legs into your socks.
• Check yourself, your children, and your pets daily for ticks. Carefully remove any ticks you find.
• Take a shower and wash and dry your clothes at high temperatures after being outdoors

Lyme disease is the most common tick-borne illness in the United States. An estimated 300,000 new cases occur every year. Lyme disease occurs in areas in which blacklegged ticks are found, primarily the northeastern states (from Virginia to Maine), the upper Midwest (Wisconsin, Minnesota, and Michigan), and parts of California and Oregon. In these regions of the United States, the incidence of Lyme disease is 10 to 100 cases per 100,000 people each year.

Lyme disease is also common in Europe, China, and Japan.

Lyme disease is caused by infection with bacteria rather than by genetic changes. The risk of developing Lyme disease is influenced by a variety of lifestyle and environmental factors that reflect how likely a person is to get bitten by an infected tick, such as where a person lives, how much time is spent outdoors, and the time of year. While there is no evidence that genetic factors play a role in susceptibility to Lyme disease, such factors may affect the severity of the disease, particularly whether antibiotic-refractory Lyme arthritis develops.

The signs and symptoms of Lyme disease result from the body's immune response to the bacteria. When the body recognizes foreign invaders, such as bacteria, it stimulates inflammation to help fight the infection. This inflammation causes the skin irritation; flu-like symptoms; and neurological, cardiac, and joint problems that characterize Lyme disease.

Certain genes that help mediate the body's immune response have been associated with the development of antibiotic-refractory Lyme arthritis. Particular variants in these genes are found more often in people with this complication than in those who do not develop it.

Some of the genes thought to be associated with the development of antibiotic-refractory Lyme arthritis provide instructions for making proteins called Toll-like receptors. As one of the first lines of defense against infection, Toll-like receptors recognize patterns that are common to many foreign invaders, rather than recognizing a specific invader, and stimulate a quick immune response that triggers inflammation. Some variants of certain Toll-like receptor genes are thought to overstimulate the body's immune response to the Lyme disease bacteria, contributing to the joint inflammation of antibiotic-resistant Lyme arthritis.

Other genes thought to be associated with antibiotic-resistant Lyme arthritis belong to a gene family called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders. Each HLA gene has many different variations, allowing each person's immune system to react to a wide range of proteins. The proteins produced from HLA genes attach to protein fragments and display them to the immune system. If the immune system recognizes the fragment as foreign or abnormal, it triggers an immune response. Some evidence suggests that certain variations of HLA genes contribute to an inappropriate immune response that causes the body to react to one of its own normal proteins. The resulting inflammation may contribute to development of antibiotic-refractory Lyme arthritis.

Normal Function

The HLA-DRB1 gene provides instructions for making a protein that plays a critical role in the immune system. The HLA-DRB1 gene is part of a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders such as viruses and bacteria.

The HLA complex is the human version of the major histocompatibility complex (MHC), a gene family that occurs in many species. The HLA-DRB1 gene belongs to a group of MHC genes called MHC class II. MHC class II genes provide instructions for making proteins that are present on the surface of certain immune system cells. These proteins attach to protein fragments (peptides) outside the cell. MHC class II proteins display these peptides to the immune system. If the immune system recognizes the peptides as foreign (such as viral or bacterial peptides), it triggers a response to attack the invading viruses or bacteria.

The protein produced from the HLA-DRB1 gene, called the beta chain, attaches (binds) to another protein called the alpha chain, which is produced from the HLA-DRA gene. Together, they form a functional protein complex called the HLA-DR antigen-binding heterodimer. This complex displays foreign peptides to the immune system to trigger the body's immune response.

Each MHC class II gene has many possible variations, allowing the immune system to react to a wide range of foreign invaders. Researchers have identified hundreds of different versions (alleles) of the HLA-DRB1 gene, each of which is given a particular number (such as HLA-DRB1*04:01).

Health Conditions Related to Genetic Changes

Alopecia areata

MedlinePlus Genetics provides information about Alopecia areata

Autoimmune Addison disease

Certain variations in the HLA-DRB1 gene have been linked to an increased risk of developing an autoimmune disorder called autoimmune Addison disease. Autoimmune disorders occur when the immune system malfunctions and attacks the body's tissues and organs. In autoimmune Addison disease, the immune system attacks the adrenal glands, which are small hormone-producing glands located on top of each kidney. Loss of hormones produced by the adrenal glands leads to the features of the condition, which include extreme tiredness (fatigue), nausea, low blood pressure (hypotension), and abnormally dark areas of skin (hyperpigmentation), especially in regions that experience a lot of friction such as the armpits, elbows, and knuckles. A particular HLA-DRB1 gene variant called HLA-DRB1*04:04 is the most well-known risk factor for autoimmune Addison disease.

Normally, the immune system responds only to proteins made by foreign invaders, not to the body's own proteins. In autoimmune Addison disease, however, an immune response is triggered by a normal adrenal gland protein; in about 85 percent of people with autoimmune Addison disease, the protein is 21-hydroxylase. 21-hydroxylase is found in the adrenal glands where it plays a key role in producing a variety of hormones that regulate many essential functions in the body. The prolonged immune attack triggered by 21-hydroxylase damages the adrenal glands (specifically the outer layers of the glands known, collectively, as the adrenal cortex), preventing hormone production. A shortage of adrenal hormones (adrenal insufficiency) disrupts several normal functions in the body, leading to the diverse features of autoimmune Addison disease. It is not clear how HLA-DRB1*04:04 and other HLA-DRB1 variations are involved in the inappropriate immune response that causes autoimmune Addison disease.

Crohn's disease

MedlinePlus Genetics provides information about Crohn's disease

Graves' disease

MedlinePlus Genetics provides information about Graves' disease

Hashimoto's disease

MedlinePlus Genetics provides information about Hashimoto's disease

Idiopathic inflammatory myopathy

MedlinePlus Genetics provides information about Idiopathic inflammatory myopathy

Idiopathic pulmonary fibrosis

MedlinePlus Genetics provides information about Idiopathic pulmonary fibrosis

Juvenile idiopathic arthritis

MedlinePlus Genetics provides information about Juvenile idiopathic arthritis

Lyme disease

MedlinePlus Genetics provides information about Lyme disease

Multiple sclerosis

Variations in the HLA-DRB1 gene have been associated with an increased risk of developing multiple sclerosis. This condition affects the brain and spinal cord (central nervous system), causing muscle weakness, poor coordination, numbness, and a variety of other health problems. One variant of this gene, called HLA-DRB1*15:01, is the most strongly linked genetic factor for the risk of multiple sclerosis.

Because the HLA-DRB1 gene is involved in the immune system, changes in it might be related to the autoimmune response and inflammation that damage nerves and the protective coating surrounding them (the myelin sheath), leading to the signs and symptoms of multiple sclerosis. However, it is unclear exactly what role HLA-DRB1 gene variants play in development of multiple sclerosis. A combination of genetic and environmental factors is likely involved in this condition.

Narcolepsy

MedlinePlus Genetics provides information about Narcolepsy

Psoriatic arthritis

MedlinePlus Genetics provides information about Psoriatic arthritis

Rheumatoid arthritis

Several common variations of the HLA-DRB1 gene are associated with a person's risk of developing rheumatoid arthritis. This disease causes chronic abnormal inflammation that primarily affects the joints. HLA-DRB1 is one of several genes in the HLA complex that have been associated with rheumatoid arthritis; variations of this gene are the most significant known genetic risk factor for the disease.

The HLA-DRB1 gene variations associated with an increased risk of rheumatoid arthritis affect single protein building blocks (amino acids) in the beta chain. These changes occur near the antigen-recognizing binding groove, which is the part of the protein that attaches (binds) to viral or bacterial peptides. This binding triggers the immune response that attacks foreign invaders. Although the mechanism by which HLA-DRB1 gene variations increase the risk of rheumatoid arthritis is unclear, researchers suspect it is related to changes in peptide binding that stimulate an abnormal immune response. However, many other genetic and environmental factors also contribute to a person's overall risk of developing rheumatoid arthritis.

A few variations of the HLA-DRB1 gene appear to decrease the risk of developing rheumatoid arthritis. It is unclear why these particular changes may be protective.

Rosacea

MedlinePlus Genetics provides information about Rosacea

Type 1 diabetes

Combinations of variations in the HLA-DRB1 gene and other HLA genes affect the risk of type 1 diabetes. Type 1 diabetes is characterized by high levels of blood glucose, also called blood sugar, resulting from a shortage of the hormone insulin and is caused by autoimmune damage to insulin-producing cells in the pancreas.

Type 1 diabetes risk is most increased by two specific combinations of variations of the HLA-DRB1 gene and other HLA genes called HLA-DQA1 and HLA-DQB1. Combinations of HLA gene variants are called HLA haplotypes. One haplotype, written as DRB1*03:01-DQA1*05:01-DQB1*02, is called DR3. The other haplotype, written as DRB1*04:01/02/04/05/08-DQA1*03:01-DQB1*02, is called DR4. People at highest risk of developing type 1 diabetes have one copy of the DR3 haplotype and one copy of the DR4 haplotype in each cell. Other HLA haplotypes only mildly increase the risk of type 1 diabetes, while some haplotypes seem to protect against developing this condition. Variations in other genes and environmental factors are also thought to affect the risk of this complex disorder.

Autoimmune disorders

Normal variations of the HLA-DRB1 gene have been associated with many other autoimmune disorders, including pemphigus, sarcoidosis, and others listed on this page. Pemphigus is a condition that causes severe blistering of the skin and mucous membranes (such as the moist lining of the mouth). Sarcoidosis is a disorder in which inflammation occurs in many organs and tissues of the body.

It is unclear how different versions of the HLA-DRB1 gene influence the risk of developing autoimmune disorders. These disorders typically result from a combination of multiple environmental and genetic factors. Changes in other HLA and non-HLA genes, some of which remain unknown, also likely contribute to the risk of developing these complex conditions.

Other Names for This Gene

• 2B13_HUMAN
• 2B1F_HUMAN
• 2B1G_HUMAN
• DRB1
• DRw10
• DW2.2/DR2.2
• HLA class II histocompatibility antigen, DR-1 beta chain
• HLA-DR1B
• HLA-DRB
• human leucocyte antigen DRB1
• lymphocyte antigen DRB1
• major histocompatibility complex, class II, DR beta 1 precursor
• MHC class II antigen
• MHC class II HLA-DR beta 1 chain
• MHC class II HLA-DR-beta cell surface glycoprotein
• MHC class II HLA-DRw10-beta
• SS1

Genomic Location

The Lyme disease bacteria causing human infection in the United States, Borrelia burgdorferi and, rarely, B. mayonii, are spread to people through the bites of infected ticks. Borrelia burgdorferi is spread primarily by the blacklegged tick (or deer tick, lxodes scapularis) in the northeastern, mid-Atlantic, and north-central United States, and by the western blacklegged tick (l. pacificus) in the Pacific Coast states. Borrelia mayonii is rarely found in ticks and has only been detected in blacklegged ticks in the north-central United States.

Blacklegged ticks have a 2-to-3-year life cycle. During this time, they go through four life stages: egg, larva, nymph, and adult. After the egg hatches, the larva and nymph each must take a blood meal to develop to the next life stage, and the female needs blood to produce eggs.

• Larval and nymphal ticks can become infected with Lyme disease bacteria when feeding on an infected wildlife host, usually a rodent. The bacteria are passed along to the next life stage. Nymphs or adult females can then spread the bacteria during their next blood meal.
• Female ticks infected with Lyme disease bacteria do not pass them to their offspring.
• Deer are important sources of blood for ticks and are important to tick survival and movement to new areas. However, deer are not infected with Lyme disease bacteria and do not infect ticks.

In most cases, a tick must be attached for 36 to 48 hours or more before the Lyme disease bacterium can be transmitted. If you remove a tick quickly (within 24 hours), you can greatly reduce your chances of getting Lyme disease.

In areas of the eastern United States where Lyme disease cases are common, people may be bitten by blacklegged ticks carrying bacteria from spring through the fall. From April through July, nymphs are actively questing for hosts in the environment, and in early spring and fall seasons, adults are most active. Nymphal ticks pose a particularly high risk due to their abundance and small size (about the size of a poppy seed), which makes them difficult to spot. In fact, Lyme disease patients are often not even aware of a tick bite before getting sick. Adult female ticks also can transmit the bacteria but because of their larger size (about the size of sesame seed), they are more likely to be noticed and removed from people before transmission of the bacteria can occur.

Lyme disease can be prevented by avoiding tick bites and promptly removing ticks.

Where are infected ticks found in the United States?

Ticks capable of spreading Lyme disease bacteria are widely distributed in forested areas across the eastern United States (I. scapularis) and in Pacific Coast states (I. pacificus). In the eastern United States, infected ticks are found primarily in the northeastern, midwestern, and mid-Atlantic states.

Are there other ways to get Lyme disease?

• A person cannot get infected from touching, kissing, or having sex with a person who has Lyme disease.
• Untreated Lyme disease during pregnancy can lead to infection of the placenta. Spread from mother to fetus is possible but rare. Fortunately, with appropriate antibiotic treatment, there is no increased risk of adverse birth outcomes. There are no published studies assessing developmental outcomes of children whose mothers acquired Lyme disease during pregnancy.
• Although no cases of Lyme disease have been linked to blood transfusion, scientists have found that the Lyme disease bacteria can live in blood that is stored for donation. Individuals being treated for Lyme disease with an antibiotic should not donate blood. Individuals who have completed antibiotic treatment for Lyme disease may be considered as potential blood donors.
• Although dogs and cats can get Lyme disease, there is no evidence that they spread the infection directly to their owners. However, pets can bring infected ticks into your home or yard. Consider protecting your pet through the use of tick and tickborne disease prevention products for animals.
• You will not get Lyme disease from eating game meat, but in keeping with general food safety principles, always cook meat thoroughly. Note that hunting and dressing game animals may bring you into close contact with infected ticks.
• There is no credible evidence that Lyme disease bacteria can be transmitted through air, food, water, or from the bites of mosquitoes, flies, fleas, or lice.
• Lone star ticks (Amblyomma americanum), the American dog tick (Dermacentor variabilis), the Rocky Mountain wood tick (D. andersoni), and the brown dog tick (Rhipicephalus sanguineus) are not known to transmit Lyme disease bacteria, however, they can transmit bacteria, parasites, and viruses that cause other tickborne diseases.

The lifecycle of blacklegged ticks (Ixodes scapularis and Ixodes pacificus) generally lasts two years. During this time, they go through four life stages: egg, six-legged larva, eight-legged nymph, and adult. After the eggs hatch, the ticks must have a blood meal at every stage to survive.

Blacklegged ticks can feed from mammals, birds, reptiles, and amphibians. The ticks need to have a new host at each stage of their life, as shown below:

How ticks find their hosts

Ticks can't fly or jump. Instead, they wait for a host, resting on the tips of grasses and shrubs in a position known as "questing". While questing, ticks hold onto leaves and grass by their lower legs. They hold their upper pair of legs outstretched, waiting to climb onto a passing host. When a host brushes the spot where a tick is waiting, it quickly climbs aboard. It then finds a suitable place to bite its host.

How ticks spread disease

The tick feeding process makes ticks very good at transmitting infection:

• Depending on the tick species and its stage of life, preparing to feed can take from 10 minutes to 2 hours. When the tick finds a feeding spot, it grasps the skin and cuts into the surface. The tick then inserts its feeding tube. Many species also secrete a cement-like substance that keeps them firmly attached during the meal. The feeding tube can have barbs which help keep the tick in place.
• Ticks also can secrete small amounts of saliva with anesthetic properties so that the animal or person can't feel that the tick has attached itself. If the tick is in a sheltered spot, it can go unnoticed.
• A blacklegged tick will attach to its host and suck the blood slowly for several days. If the host animal has certain bloodborne infections, such as the Lyme disease agent, the tick may ingest the pathogen and become infected. If the tick later feeds on a human, that human can become infected.
• After feeding, the blacklegged tick drops off and prepares for the next life stage. At its next feeding, it can then transmit the infection to the new host. Once infected, a tick can transmit infection throughout its life.
• If you remove a tick quickly (within 24 hours) you can greatly reduce your chances of getting Lyme disease. It takes some time for the Lyme disease-causing bacteria to move from the tick to the host. The longer the tick is attached, the greater the risk of acquiring disease from it.

I've been bitten by a tick. Do I have Lyme disease?

If you have not done so already, remove the tick with fine-tipped tweezers.

The chances that you might get Lyme disease from a single tick bite depend on the type of tick, where you acquired it, and how long it was attached to you. Many types of ticks bite people in the U.S., but only blacklegged ticks transmit the bacteria that cause Lyme disease. Furthermore, only blacklegged ticks in the highly endemic areas of the northeastern and north central U.S. are commonly infected. Finally, blacklegged ticks need to be attached for at least 24 hours before they can transmit Lyme disease. This is why it’s so important to remove them promptly and to check your body daily for ticks if you live in an endemic area.

If you develop illness within a few weeks of a tick bite, see your health care provider right away. Common symptoms of Lyme disease include a rash, fever, body aches, facial paralysis, and arthritis. Ticks can also transmit other diseases, so it’s important to be alert for any illness that follows a tick bite.

Can Lyme disease be transmitted sexually?

There is no credible scientific evidence that Lyme disease is spread through sexual contact. Published studies in animals do not support sexual transmission (Moody 1991; Woodrum 1999), and the biology of the Lyme disease spirochete is not compatible this route of exposure (Porcella 2001). The ticks that transmit Lyme disease are very small and easily overlooked. Consequently, it is possible for sexual partners living in the same household to both become infected through tick bites, even if one or both partners doesn’t remember being bitten.

Can Lyme disease be transmitted through breast milk?

There are no reports of Lyme disease being spread to infants through breast milk. If you are diagnosed with Lyme disease and are also breastfeeding, make sure that your doctor knows this so that he or she can prescribe an antibiotic that’s safe for use when breastfeeding.

Can Lyme disease be transmitted during a blood transfusion?

Although no cases of Lyme disease have been linked to blood transfusion, scientists have found that the Lyme disease bacteria can live in blood from a person with an active infection that is stored for donation. Individuals being treated for Lyme disease with an antibiotic should not donate blood. Individuals who have completed antibiotic treatment for Lyme disease may be considered as potential blood donors. The Red Cross provides additional information on the most recent criteria for blood donation.

Is it true that you can get Lyme disease anywhere in the U.S.?

No. Lyme disease is spread through the bite of a blacklegged tick (Ixodes scapularis or Ixodes pacificus) that is infected with Borrelia burgdorferi. In the United States, most infections occur in the following endemic areas:

• Northeast and mid-Atlantic, from northeastern Virginia to Maine
• North central states, mostly in Wisconsin and Minnesota
• West Coast, particularly northern California

Maps showing the distribution of human cases are based on where people live, which because of travel, is not necessarily where they became infected. Cases are sometimes diagnosed and reported from an area where Lyme disease is not expected, but they are almost always travel-related.

I live in the southeastern U.S. and get a lot of lone star tick bites. I've heard that I can get “southern Lyme disease”. Is this true?

The lone star tick is primarily found in the southeastern and eastern United States. Lone star ticks do not transmit Lyme disease. However, you are correct to be concerned about this very aggressive species. The lone star tick (Amblyomma americanum) can spread human ehrlichiosis, tularemia, and Southern Tick-Associated Rash Illness (STARI).

The rash of STARI is a red, expanding “bull’ s eye” lesion that develops around the site of a lone star tick bite. The rash usually appears within seven days of tick bite and expands to a diameter of 8 centimeters (3 inches) or more. The rash should not be confused with much smaller areas of redness and discomfort that can occur commonly at tick bite sites. Unlike Lyme disease, STARI has not been linked to arthritis, neurological problems, or chronic symptoms. Nevertheless, the similarity between the STARI bull’s eye rash and the Lyme disease bull’s eye rash has created much public confusion. The pathogen responsible for STARI has not been identified.

In contrast, Lyme disease in North America is caused by a specific type of bacteria, Borrelia burgdorferi, which is transmitted by two species of blacklegged ticks, Ixodes scapularis and Ixodes pacificus. While blacklegged ticks exist in the southern U.S., their feeding habits in this region make them much less likely to maintain, sustain, and transmit Lyme disease.

Seek medical attention if you observe any of these symptoms and have had a tick bite, live in an area known for Lyme disease, or have recently traveled to an area where Lyme disease occurs.

Untreated Lyme disease can produce a wide range of symptoms, depending on the stage of infection. These include fever, rash, facial paralysis, and arthritis.

Early Signs and Symptoms (3 to 30 Days After Tick Bite)

• Fever, chills, headache, fatigue, muscle and joint aches, and swollen lymph nodes may occur in the absence of rash
• Erythema migrans (EM) rash:
  • Occurs in approximately 70 to 80 percent of infected persons
  • Begins at the site of a tick bite after a delay of 3 to 30 days (average is about 7 days)
  • Expands gradually over several days reaching up to 12 inches or more (30 cm) across
  • May feel warm to the touch but is rarely itchy or painful
  • Sometimes clears as it enlarges, resulting in a target or “bull’s-eye” appearance
  • May appear on any area of the body
  • Does not always appear as a “classic” erythema migrans rash

Later Signs and Symptoms (days to months after tick bite)

• Severe headaches and neck stiffness
• Additional EM rashes on other areas of the body
• Facial palsy (loss of muscle tone or droop on one or both sides of the face)
• Arthritis with severe joint pain and swelling, particularly the knees and other large joints.
• Intermittent pain in tendons, muscles, joints, and bones
• Heart palpitations or an irregular heart beat (Lyme carditis)
• Episodes of dizziness or shortness of breath
• Inflammation of the brain and spinal cord
• Nerve pain
• Shooting pains, numbness, or tingling in the hands or feet

More about rashes

• A small bump or redness at the site of a tick bite that occurs immediately and resembles a mosquito bite, is common. This irritation generally goes away in 1-2 days and is not a sign of Lyme disease.
• A rash with a very similar appearance to EM occurs with Southern Tick-associated Rash Illness (STARI), but is not Lyme disease
• Ticks can spread other organisms that may cause a different type of rash.

When assessing a patient for Lyme disease, health care providers should consider:

• The signs and symptoms of Lyme disease
• The likelihood that the patient has been exposed to infected blacklegged ticks
• The possibility that other illnesses may cause similar symptoms
• Results of laboratory tests, when indicated

Laboratory testing

CDC currently recommends a two-step testing process for Lyme disease. Both steps are required and can be done using the same blood sample. If this first step is negative, no further testing is recommended. If the first step is positive or indeterminate (sometimes called “equivocal”), the second step should be performed. The overall result is positive only when the first test is positive (or equivocal) and the second test is positive (or for some tests equivocal).

 Key points to remember

• Most Lyme disease tests are designed to detect antibodies made by the body in response to infection.
• Antibodies can take several weeks to develop, so patients may test negative if infected only recently.
• Antibodies normally persist in the blood for months or even years after the infection is gone; therefore, the test cannot be used to determine cure.
• Infection with other diseases, including some tickborne diseases, or some viral, bacterial, or autoimmune diseases, can result in false positive test results.
• Some tests give results for two types of antibody, IgM and IgG. Positive IgM results should be disregarded if the patient has been ill for more than 30 days.