Lyme disease is a tick-borne disease caused by bacteria that infected ticks pass to you during a bite. In the United States, black-legged ticks, often called deer ticks, spread the disease in the Northeast, Mid-Atlantic, North-Central, and parts of the Pacific Coast.
Ticks do not create Lyme disease themselves. They spread bacteria after acquiring them from infected wildlife, and prompt tick removal can greatly reduce your risk.
Knowing which ticks transmit Lyme disease, where exposure occurs, and which symptoms need medical attention helps you respond sooner after a tick bite.
How Infection Moves From Wildlife to People
Bacteria, wildlife hosts, and ticks maintain the Lyme disease cycle. Ticks usually acquire the bacteria from small mammals, then pass them to another animal or person during a later blood meal.
The Bacteria Behind Lyme Disease
Borrelia burgdorferi is the main Lyme disease bacterium in the United States. Borrelia mayonii can also cause illness in parts of the Upper Midwest.
Infected ticks transfer these bacteria through their saliva while feeding. The black-legged tick, Ixodes scapularis, spreads Lyme disease in much of the eastern and north-central United States.
The western black-legged tick, Ixodes pacificus, transmits it along parts of the Pacific Coast, as explained by the Centers for Disease Control and Prevention.
Why Blacklegged Ticks Become Infected
Blacklegged ticks develop through egg, larva, nymph, and adult stages. Larvae and nymphs need blood meals to grow, and they can pick up Borrelia while feeding on infected wildlife.
White-footed mice and chipmunks often carry the bacteria that infect feeding ticks. An infected nymph or adult female can then transmit the bacteria during its next blood meal.
The Different Roles of Rodents and Deer
Rodents maintain the Lyme disease cycle by infecting young ticks. Deer support tick survival and movement by providing blood meals and carrying ticks across landscapes.
Deer do not usually carry Borrelia burgdorferi in a way that infects ticks. Their role is ecological, while rodents commonly serve as the bacterial reservoir.
Why Some Tick Bites Carry More Risk
Your risk after a tick bite depends on the tick species, whether it carries Lyme bacteria, where you encountered it, and how long it stayed attached. Fast tick removal and early detection can reduce the chance of infection.
Attachment Time and Bacterial Transmission
An infected tick generally needs to remain attached for more than 24 hours before transmission becomes likely. Remove any tick as soon as you find it rather than waiting to identify it.
Use fine-tipped tweezers to grasp the tick close to your skin and pull upward steadily. Clean the bite area and your hands afterward.
Do not twist, crush, or cover the tick with petroleum jelly, heat, or chemicals.
Why Nymphs Are Easy to Miss
Nymphal ticks are about the size of a poppy seed, making them difficult to spot on skin, clothing, or hair. They are active during warmer months and account for many unnoticed exposures.
Adult ticks are larger, roughly sesame-seed-sized, so you may notice and remove them sooner.
Adult females can transmit Lyme disease, though visibility may shorten their attachment time.
Where and When Exposure Is Most Likely
You can encounter blacklegged ticks in wooded areas, leaf litter, brush, tall grass, and places where vegetation meets a trail. In the eastern United States, nymphs are especially active from spring into midsummer.
Adults are commonly active in early spring and fall. Check your body after outdoor activity, even if you stayed on a path.
Ticks can crawl from clothing to exposed skin before attaching.
Recognizing Illness and Getting Care Early
Lyme disease symptoms can appear days to weeks after a bite and may change as infection spreads. A healthcare professional evaluates your exposure, symptoms, geography, and test results rather than relying on a tick bite alone.
Early Signs After a Possible Exposure
The classic early rash, called erythema migrans, gradually expands and may resemble a bull’s-eye, though it does not always have that appearance. It may feel warm but often is not painful or itchy.
Other early symptoms include fever, headache, fatigue, muscle or joint pain, and other flu-like symptoms. Contact a healthcare professional if these symptoms occur after time outdoors or a possible tick bite, even if you never saw a tick.
How Symptoms Can Progress
Early localized disease can progress to early disseminated Lyme disease, sometimes causing multiple rashes, facial weakness, severe headache, neck stiffness, pain, numbness, or other neurological problems. Heart involvement, called Lyme carditis, can cause palpitations, dizziness, fainting, or heart block.
Untreated infection may lead to late disseminated disease, including arthritis, particularly in a swollen knee or other large joint. Some people report lingering fatigue, pain, or concentration problems after treatment, known as post-Lyme disease syndrome.
Testing and Antibiotic Options
Healthcare professionals may diagnose Lyme disease based on symptoms and exposure, especially when a typical erythema migrans rash is present. Blood tests look for Lyme antibodies, which may not be detectable early in infection.
Doctors may prescribe antibiotics such as doxycycline, amoxicillin, or cefuroxime when treatment is appropriate. Severe neurological or cardiac disease may require intravenous ceftriaxone.
Reducing Exposure to Lyme-Carrying Ticks
You can lower your risk by combining protective clothing, EPA-registered tick repellent, regular checks, and quick tick removal. These steps also help protect you from other tick-borne diseases.
Personal Protection Outdoors
Wear long pants, long sleeves, and light-colored clothing so ticks are easier to see. Tuck pants into socks when walking through brush or tall grass, and stay near the center of maintained trails.
Products containing DEET, picaridin, IR3535, oil of lemon eucalyptus, or para-menthane-diol can repel ticks when used according to the label. Treat clothing and gear with permethrin, following product directions and keeping permethrin-treated items away from cats while wet.
Checking for and Removing Ticks
After being outdoors, inspect your legs, waist, armpits, groin, scalp, behind your ears, and the backs of your knees. Showering soon after coming inside can help remove unattached ticks.
Put clothing in a hot dryer before washing when possible, since heat can kill ticks. If you find an attached tick, use fine-tipped tweezers for prompt tick removal, then monitor the bite area and your health.
Other Illnesses Ticks Can Spread
Lyme disease is only one of several tick-borne diseases. Depending on the tick and region, you may also face exposure to babesiosis, anaplasmosis, ehrlichiosis, Rocky Mountain spotted fever, or relapsing fever.
Different regions use names like lone star tick, castor bean tick, and sheep tick for various tick species. Not every species transmits Lyme disease.
Tell your healthcare professional where you traveled and when the bite occurred. Symptoms and risks vary by tick and location.
