Lyme Disease: A Tick-Borne Bacterial Infection
What Is Lyme Disease?
Lyme disease is a bacterial infection spread to people through the bite of infected blacklegged ticks.
In the United States, Lyme disease is caused primarily by Borrelia burgdorferi and, more rarely, Borrelia mayonii.
Lyme disease occurs most commonly in the Northeast, mid-Atlantic, and upper Midwest, although cases also occur in some areas along the Pacific Coast.
Lyme disease is the leading cause of tickborne disease in the United States. CDC estimates that approximately 476,000 people may be diagnosed and treated for Lyme disease each year in the United States. This estimate likely includes some people treated based on clinical suspicion who may not actually have Lyme disease.
Lyme disease has been a nationally notifiable condition in the United States since 1991.
Early diagnosis and appropriate antibiotic treatment are important because untreated Lyme disease can spread to the joints, heart, and nervous system.
Which Ticks Spread Lyme Disease?
Two species of blacklegged ticks transmit Lyme disease bacteria to people in the United States:
- Blacklegged tick or deer tick (Ixodes scapularis) — primarily in the northeastern, mid-Atlantic, and north-central United States
- Western blacklegged tick (Ixodes pacificus) — in areas along the Pacific Coast
Blacklegged ticks have four life stages:
- Egg
- Larva
- Nymph
- Adult
Their life cycle generally takes two to three years.
Larval and nymphal ticks can become infected with Lyme disease bacteria while feeding on an infected wildlife host, usually a rodent. The bacteria can remain in the tick as it develops into its next life stage. Infected nymphs or adult females can then transmit the bacteria during a later blood meal.
What Role Do Deer Play?
Deer are important sources of blood for ticks and contribute to tick survival and movement to new areas.
However, deer are not infected with Lyme disease bacteria and do not infect ticks with Lyme disease bacteria. Deer therefore should not be described as reservoirs for the bacteria that cause Lyme disease.
How Long Does a Tick Need to Be Attached to Transmit Lyme Disease?
According to current CDC guidance, in most cases an infected tick must be attached for more than 24 hours before Lyme disease bacteria can be transmitted.
Removing an attached tick within 24 hours can greatly reduce the chance of developing Lyme disease. Prompt tick checks and prompt removal are therefore important.
Nymphal blacklegged ticks pose a particularly high risk because they are abundant and extremely small—approximately the size of a poppy seed—which can make them difficult to notice.
In areas of the eastern United States where Lyme disease is common, nymphs are especially active from approximately April through July.
Where Are You Most Likely to Encounter Ticks?
Ticks commonly live in grassy, brushy, or wooded areas and may also be found on animals.
People can encounter ticks while:
- Hiking
- Camping
- Gardening
- Hunting
- Walking dogs
- Performing yard work
- Spending time around wooded or brushy areas
Tick exposure is not limited to wilderness areas. Many people who develop Lyme disease are exposed to infected ticks in their own yards or neighborhoods.
Tick exposure can occur year-round, although ticks are generally most active during warmer months.
What Are the Early Symptoms of Lyme Disease?
Early signs and symptoms may begin approximately 3 to 30 days after an infected tick bite.
Possible symptoms include:
- Fever
- Chills
- Headache
- Fatigue
- Muscle aches
- Joint aches
- Swollen lymph nodes
- Erythema migrans (EM) rash
These symptoms can occur with or without a rash.
What Does the Lyme Disease Rash Look Like?
The characteristic Lyme disease rash is called erythema migrans (EM).
CDC reports that EM occurs in approximately 70–80% of infected people. It usually begins at the site of the tick bite 3–30 days after the bite, with an average onset of about seven days.
The rash generally expands gradually over several days. It may feel warm to the touch but is rarely itchy or painful.
Some EM rashes develop central clearing and resemble a target or “bull’s-eye,” but many Lyme disease rashes do not have a classic bull’s-eye appearance. Their appearance can vary considerably.
A small bump or area of redness that appears immediately after a tick bite and disappears within a day or two is common and, by itself, is not considered a sign of Lyme disease.
What Can Happen if Lyme Disease Is Not Treated?
Without appropriate treatment, Lyme disease can spread to other parts of the body.
Later signs and symptoms can include:
- Severe headaches and neck stiffness
- Additional EM rashes
- Facial palsy or facial drooping
- Severe joint pain and swelling, particularly in the knees and other large joints
- Nerve pain
- Shooting pains, numbness, or tingling
- Inflammation of the brain and spinal cord
- Heart palpitations or an irregular heartbeat
- Dizziness or shortness of breath
Lyme Arthritis
Lyme arthritis can cause obvious swelling of one or a few joints, most commonly the knee.
If left untreated, permanent joint damage can occur.
Neurologic Lyme Disease
Neurologic Lyme disease can cause symptoms such as:
- Facial palsy
- Numbness
- Pain
- Weakness
- Shooting pain
- Symptoms of meningitis, such as fever, stiff neck, and severe headache
Most people with Lyme disease respond well to appropriate antibiotics and fully recover. However, varying degrees of permanent nervous-system damage may develop in some people who do not receive treatment in the early stages of illness and whose disease progresses.
Lyme Carditis
Lyme carditis occurs when Lyme disease bacteria enter tissues of the heart and interfere with the normal movement of the heart’s electrical signals.
Symptoms can include:
- Light-headedness
- Fainting
- Shortness of breath
- Heart palpitations
- Chest pain
CDC reports Lyme carditis in approximately 1 out of every 100 Lyme disease cases reported to CDC.
Lyme carditis can be serious. Suspected severe Lyme carditis requires prompt medical evaluation and may require hospitalization, cardiac monitoring, and intravenous antibiotics.
How Is Lyme Disease Diagnosed?
Healthcare providers consider several factors when evaluating someone for Lyme disease, including:
- Possible exposure to infected blacklegged ticks
- Whether symptoms are clinically consistent with Lyme disease
- Other illnesses that could cause similar symptoms
- Laboratory test results when testing is appropriate
CDC recommends a two-step serologic testing process using FDA-cleared antibody tests when laboratory testing is indicated.
With standard two-tier testing, the first step uses an enzyme immunoassay (EIA), followed when appropriate by western blotting (WB).
Increasingly, laboratories use modified two-tier testing, in which both steps use EIAs.
Antibody tests can be falsely negative early in infection because antibodies take time to develop. CDC notes that serologic tests may be falsely negative during approximately the first 4–6 weeks after infection.
For a person with appropriate tick exposure who develops a skin lesion clinically compatible with erythema migrans, current clinical guidelines recommend making the diagnosis based on the clinical presentation rather than relying on laboratory testing for confirmation.
How Is Lyme Disease Treated?
Lyme disease is treated with antibiotics.
Commonly used antibiotics include:
- Doxycycline
- Amoxicillin
- Cefuroxime axetil
The specific medication and duration of treatment depend on factors such as:
- Symptoms and clinical manifestation
- Age
- Allergies
- Pregnancy status
- Other individual medical considerations
CDC states that most cases of Lyme disease can be treated with 10 days to 4 weeks of antibiotics, depending on the clinical situation.
People appropriately treated during the early stages usually recover rapidly and completely.
The appropriate treatment regimen depends on the particular clinical manifestation, severity of illness, and patient-specific factors. Some neurologic manifestations and more severe Lyme carditis may require intravenous antibiotics, while many other manifestations can be treated with oral antibiotics.
Can Antibiotics Be Given After a Tick Bite?
Antibiotics are not automatically recommended after every tick bite.
In certain circumstances, a single dose of doxycycline after a tick bite may reduce the risk of developing Lyme disease. CDC advises discussing with a healthcare provider whether post-exposure antibiotics are appropriate.
Clinical guidelines recommend single-dose doxycycline prophylaxis for appropriately identified high-risk Ixodes tick bites when treatment can be started within 72 hours after tick removal and other relevant criteria are met.
A healthcare professional should determine whether preventive antibiotics are appropriate for an individual patient.
What Is Post-Treatment Lyme Disease Syndrome?
Most people recover after appropriate antibiotic treatment. However, some people experience prolonged symptoms such as:
- Fatigue
- Body aches or pain
- Difficulty thinking or concentrating
CDC refers to prolonged symptoms due to Lyme disease following treatment as Post-Treatment Lyme Disease Syndrome (PTLDS).
The cause of PTLDS is currently unknown.
CDC discourages use of the term “Chronic Lyme Disease” when it implies that prolonged symptoms are caused by an ongoing bacterial infection, because the cause of these prolonged symptoms is not currently known.
Studies have generally found that extended antibiotic treatment is no better than placebo for treating prolonged symptoms after recommended Lyme disease treatment. Long-term antibiotic use can also cause serious and even potentially life-threatening complications.
People who continue to experience prolonged or recurring symptoms should work with a healthcare professional to investigate possible causes and develop an individualized care plan.
How Can You Prevent Lyme Disease?
The best way to prevent Lyme disease is to prevent tick bites.
CDC recommends measures including:
- Avoiding wooded, brushy, or grassy areas where ticks live when practical
- Walking in the center of trails
- Using an EPA-registered insect repellent containing DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone
- Treating clothing and gear with products containing 0.5% permethrin
- Checking clothing, gear, pets, children, and your body for ticks after spending time outdoors
- Showering soon after coming indoors
- Removing attached ticks promptly
Always follow product-label instructions.
Products containing oil of lemon eucalyptus (OLE) or para-menthane-diol (PMD) should not be used on children younger than 3 years old.
Permethrin products intended for tick prevention should be used on clothing and gear according to their label directions and should not be applied directly to the skin.
How Should You Remove an Attached Tick?
Remove an attached tick as soon as possible.
CDC recommends:
- Use clean fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible.
- Pull the tick away from the skin using steady, even pressure.
- Do not twist or jerk the tick.
- Dispose of the tick by placing it in a sealed container, wrapping it tightly in tape, flushing it down the toilet, or putting it in alcohol.
- Clean the bite area and your hands with soap and water, rubbing alcohol, or hand sanitizer.
- Check your body carefully for additional ticks.
Fine-tipped tweezers are preferred. If they are unavailable, regular tweezers can also be used.
Do not use petroleum jelly, heat, nail polish, or similar substances in an attempt to make a tick detach.
Should You Have a Removed Tick Tested?
CDC generally does not recommend commercial testing of removed ticks to guide treatment decisions.
Reasons include:
- A positive test on the tick does not mean the person was infected.
- A negative result can provide false reassurance.
- Laboratories that conduct tick testing are not required to meet the same high standards of quality control used by clinical diagnostic laboratories.
- Treatment decisions should not be based on tick-testing results.
What Should You Do After a Tick Bite?
After removing the tick:
- Clean the bite area and your hands.
- Check your body carefully for additional ticks.
- Watch for symptoms during the following days and weeks.
- Contact a healthcare professional if you develop a rash, fever, or other concerning symptoms.
- Tell the healthcare professional about the tick bite, when it occurred, and where you most likely encountered the tick.
Can Lyme Disease Spread From Person to Person?
There is no credible scientific evidence that Lyme disease spreads through ordinary person-to-person contact such as:
- Touching
- Kissing
- Sexual contact
There is also no credible evidence that Lyme disease bacteria are transmitted through:
- Air
- Food
- Water
- Mosquito bites
- Fly bites
- Flea bites
- Lice
CDC states that there are no reports of Lyme disease being spread to infants through breast milk.
Lyme Disease and Pregnancy
Untreated Lyme disease during pregnancy can result in infection of the placenta.
Transmission from mother to fetus is possible but extremely rare.
CDC states that with appropriate antibiotic treatment, there is no increased risk of adverse birth outcomes.
Anyone who is pregnant and suspects Lyme disease should contact a healthcare professional promptly so that an appropriate antibiotic and treatment plan can be selected.
Can You Get Lyme Disease Again?
Yes.
Having Lyme disease once does not provide reliable protection against future infection. A person can develop Lyme disease again after another bite from an infected tick. Lyme antibodies can remain detectable for months or years but do not reliably prevent reinfection.
People who develop new symptoms after previously having Lyme disease should be evaluated by a healthcare professional rather than assuming the symptoms represent either reinfection or persistent infection.
Are Natural Remedies Effective for Lyme Disease?
There is no natural or alternative therapy that has been shown to cure Lyme disease.
The National Center for Complementary and Integrative Health states that antibiotics are the only known effective treatment for Lyme disease.
Alternative approaches promoted as Lyme disease “cures,” including nutritional, herbal, oxygen, energy, or essential-oil therapies, have not been demonstrated to cure Lyme disease, and some may be harmful.
Natural or alternative remedies should not replace appropriate antibiotic treatment prescribed by a qualified healthcare professional.
Can Pets Spread Lyme Disease to People?
Dogs and cats can develop Lyme disease, but there is no evidence that pets directly transmit Lyme disease to people.
Pets can, however, carry ticks into the home or yard, where those ticks may later attach to people.
Check pets regularly for ticks and discuss appropriate tick-prevention products with a veterinarian.
How Can You Reduce Ticks Around Your Yard?
It is not possible to guarantee a completely tick-free yard, but landscaping measures can help reduce tick habitat.
Recommended measures include:
- Removing leaf litter
- Clearing tall grasses and brush
- Mowing the lawn regularly
- Creating approximately a 3-foot-wide barrier of wood chips or gravel between lawns and wooded areas
- Keeping playground equipment, decks, and patios away from wooded or brushy yard edges
- Keeping wood stacked neatly in a dry area
How Should You Check for Ticks After Being Outdoors?
Perform a full-body tick check after returning from areas where ticks may be present.
Pay particular attention to:
- Under the arms
- In and around the ears
- Inside the belly button
- Behind the knees
- In and around the hair
- Between the legs
- Around the waist
Also check:
- Children
- Pets
- Clothing
- Coats
- Backpacks
- Outdoor gear
CDC notes that showering within two hours after coming indoors has been shown to reduce the risk of Lyme disease and provides a useful opportunity to check for ticks.
Does Climate Affect Lyme Disease Risk?
Climate and weather are among several factors that can influence ticks and vector-borne disease risk.
CDC notes that vector-borne disease transmission can also be influenced by factors including:
- Local weather conditions
- Human modification of the landscape
- Diversity and availability of animal hosts
- Human behavior that affects contact between people and vectors
Climate change can influence the distribution and activity of disease vectors, including ticks. However, Lyme disease ecology is complex, and changes in Lyme disease risk should not be attributed to climate alone because land use, wildlife populations, human behavior, prevention practices, and other ecological factors also influence risk.
Important 2026 Update: Borrelia mayonii Detected in New York
Borrelia mayonii is a much less common cause of Lyme disease than Borrelia burgdorferi.
On June 4, 2026, CDC published an MMWR report describing an investigation involving a New York resident with no reported travel who tested positive for B. mayonii.
Investigators subsequently detected B. mayonii in Ixodes scapularis ticks collected from the patient’s property in Herkimer County, New York.
CDC described the findings as the first detection of B. mayonii in New York State, with the investigation indicating local tickborne transmission at the patient’s property.
Before this investigation, B. mayonii had been identified in people and ticks in Minnesota and Wisconsin.
The New York finding does not establish that B. mayonii is widespread throughout New York State. In the investigation, additional ticks collected during 2021–2025 from 23 other New York counties tested negative for B. mayonii; the positive ticks were detected at the Herkimer County case property.
Is There a Lyme Disease Vaccine?
Pfizer and Valneva are developing an investigational 6-valent OspA-based Lyme disease vaccine candidate known as PF-07307405 (LB6V), formerly VLA15. The candidate has completed Phase 3 human trials.
On March 23, 2026, Pfizer and Valneva reported topline results from the Phase 3 VALOR trial involving participants 5 years of age and older.
The two prespecified analyses produced company-reported vaccine efficacy estimates of:
- 73.2%
- 74.8%
However, fewer Lyme disease cases occurred during the study than anticipated.
The first prespecified analysis, which was the trial’s primary endpoint, did not meet its predetermined statistical criterion. The second prespecified analysis met the specified statistical criterion.
On August 14, 2026, Pfizer and Valneva announced that the European Medicines Agency (EMA) had validated the Marketing Authorization Application (MAA) for PF-07307405 and would begin its assessment of the application.
Validation of the application means the regulatory assessment process can proceed; it does not mean the vaccine has been approved.
LB6V remains investigational and is not currently available for routine use.
The Bottom Line
Lyme disease is a tick-borne bacterial infection that is usually treatable with appropriate antibiotics, particularly when recognized and treated early.
Important steps include:
- Prevent tick bites whenever possible.
- Perform tick checks after spending time outdoors.
- Remove attached ticks promptly.
- Use clean fine-tipped tweezers when available.
- Watch for a rash, fever, or other symptoms following a tick bite.
- Seek medical evaluation when concerning symptoms develop.
- Follow evidence-based testing and treatment recommendations.
Prompt and proper tick removal can reduce the risk of Lyme disease. CDC recommends grasping an attached tick close to the skin and removing it using steady, even pressure.
More Resources
- Your Ultimate Guide to Tackling Ticks
- How to Safely Remove Ticks
- Tick Check Yourself!
- Tick Identification Guide
- Tick Prevention Tips
- Tick Wars
- Protecting Your Pets From Ticks
- Frequently Asked Questions
Educational Disclaimer
This information is provided for educational purposes only and is not intended to replace professional medical advice, diagnosis, or treatment.
If you develop a fever, rash, unusual fatigue, headache, body aches, nausea, vomiting, or other concerning symptoms following a known or possible tick exposure, contact a qualified healthcare provider and mention the potential tick exposure.
