Bacterial illness
Lyme Disease
Lyme disease is a bacterial infection caused by Borrelia burgdorferi and, rarely, B. mayonii. It spreads through the bite of an infected blacklegged tick, also called the deer tick. It is the most commonly reported tick-borne illness in the US. Most cases are in the Northeast, mid-Atlantic, and upper Midwest, with a smaller pocket on the Pacific Coast. Note: Lyme disease is NOT spread by the Lone Star tick. Most people who are diagnosed and treated early recover fully with a standard course of antibiotics.
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What it is
Lyme disease is caused by Borrelia bacteria, which spread to people through the bite of an infected tick. In the eastern and central US, this is the blacklegged tick (Ixodes scapularis). Along the Pacific Coast, it is the western blacklegged tick (Ixodes pacificus). CDC says a tick generally must be attached for more than 24 hours before it can pass on Lyme bacteria. That is why finding and removing ticks quickly lowers risk. Lyme disease is different from the illnesses our readers most often ask about with the Lone Star tick. The Lone Star tick (Amblyomma americanum) does not spread Lyme disease. But a Lone Star tick bite can cause a round, growing rash that looks like the Lyme rash. This is a separate condition called Southern Tick-Associated Rash Illness (STARI). This page is for learning. It does not replace a doctor's advice, diagnosis, or treatment.
Symptoms
- Erythema migrans (EM): a growing red rash at the bite site, sometimes shaped like a target or bull's-eye. About 70–80% of people get it (CDC)
- Fever and chills
- Fatigue
- Headache
- Muscle and joint aches
- Swollen lymph nodes
- Later: arthritis with joint pain and swelling, especially in the knees
- Later: facial palsy (drooping on one or both sides of the face)
- Later: heart palpitations or an irregular heartbeat (Lyme carditis)
- Later: shooting pains, numbness, or tingling in the hands or feet
How soon symptoms appear
The rash (erythema migrans) usually appears 3 to 30 days after the tick bite, about 7 days on average (CDC). Later signs, such as arthritis, facial palsy, or Lyme carditis, can develop days to months after an infection that is not treated.
Diagnosis
Doctors diagnose Lyme disease based on symptoms, signs such as the rash, and possible contact with ticks where Lyme disease occurs. When lab tests are used, CDC recommends a validated two-step antibody blood test. These tests can be falsely negative in the first few weeks of infection. So a person with a classic rash and likely exposure is often treated right away, without waiting for test results. Testing is a medical decision. A doctor should read the results in light of your symptoms and exposure.
Treatment
Lyme disease is treated with antibiotics. Most people recover quickly and fully when treatment starts early. For the rash stage in adults, CDC describes antibiotic pills including doxycycline, amoxicillin, or cefuroxime axetil. The shortest course that works is generally preferred, to limit side effects. CDC lists azithromycin as a less effective option for people who cannot take the first-choice drugs. Medicines, doses, and treatment length differ for children, during pregnancy, and for later-stage disease. These are decisions for a licensed doctor. This section is for learning only and leaves out doses on purpose. A small number of people report lasting fatigue, pain, or trouble focusing for months after treatment. This is sometimes called Post-Treatment Lyme Disease Syndrome. The cause is not fully understood, and studies have not shown that longer antibiotic courses help.
Prevention
The best protection is avoiding tick bites. Use EPA-registered insect repellents on bare skin, such as those with DEET, picaridin, IR3535, or oil of lemon eucalyptus. Treat clothing and gear with products containing 0.5% permethrin. Avoid wooded and brushy areas with high grass and leaf litter, and walk in the center of trails. After being outdoors, check your whole body for ticks. Include the scalp, behind the ears and knees, the armpits, and the groin. Shower within about two hours. Tumble dry clothing on high heat for at least 10 minutes to kill any ticks. If you find an attached tick, remove it right away with clean, fine-tipped tweezers.
Where it occurs
In the US, Lyme disease is concentrated in the Northeast, mid-Atlantic, and upper Midwest, where the blacklegged tick (Ixodes scapularis) is established. A separate, smaller pocket is found along the Pacific Coast. There, the western blacklegged tick (Ixodes pacificus) spreads it. Cases are much less common in the South and South-Central states, where the Lone Star tick is the main tick. The Lone Star tick does not spread Lyme disease.
When to seek care
Contact a doctor if you get a growing rash, fever, or flu-like symptoms within several weeks of a tick bite or time spent where Lyme disease occurs. Do this even if you never saw a tick. Get care more urgently for signs of later disease, such as facial drooping or a severe headache with a stiff neck. Heart symptoms also need urgent care: palpitations, an irregular heartbeat, shortness of breath, chest pain, fainting, or dizziness. These can be signs of Lyme carditis. When in doubt, call your doctor. Getting checked and treated early gives the best results. For emergencies such as trouble breathing or anaphylaxis, call emergency services.
Common questions
Can a Lone Star tick give me Lyme disease?
No. Blacklegged (deer) ticks spread Lyme disease in the eastern and central US, and western blacklegged ticks spread it on the Pacific Coast. The Lone Star tick does not. A Lone Star tick bite can cause a round, growing rash that looks like the Lyme rash. That condition is called STARI (Southern Tick-Associated Rash Illness), and it is a separate illness.
Does the rash always look like a bull's-eye?
No. The rash appears in about 70–80% of people with Lyme disease (CDC), and it does not always form a classic bull's-eye. It can be a solid red patch that grows. Some people never notice a rash at all, so other symptoms and possible exposure matter too.
How long must a tick be attached to transmit Lyme disease?
Usually more than 24 hours. CDC says that, in general, a blacklegged tick must be attached for more than 24 hours before it can pass on Lyme bacteria. Some other sources cite a longer window of roughly 36 to 48 hours. This is why checking for ticks and removing them quickly lowers your risk. Ask a doctor about your own situation.
Will I have long-term problems after Lyme disease?
Usually not, if it is treated early. Most people treated early recover fully. A minority report lasting fatigue, pain, or trouble focusing for months afterward. This is sometimes called Post-Treatment Lyme Disease Syndrome. The cause isn't fully understood, and research has not shown that long courses of antibiotics help.
Can Lyme disease be prevented right after a tick bite?
Sometimes. Removing an attached tick quickly and correctly is the most important step. In some cases, a doctor may consider a single preventive dose of antibiotic. This depends on the type of tick, how long it was attached, and the local Lyme risk. Talk this over with a doctor.
Sources
- 1.Lyme Disease (opens in a new tab) · CDC
Spread by blacklegged (deer) ticks, NOT the Lone Star tick. Early sign is often an expanding erythema migrans rash.
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This page is here to help you learn. It is not medical advice. Only a doctor can diagnose a tick-borne illness. Read our sources and disclaimer.