The tick infects the person with the bacterium Borrelia burgdorferi (B. burgdorferi).
At first, a rash may appear. This can disappear without treatment, but in time, the person may develop problems with the joints, the heart, and the nervous system.
Lyme disease is the most common tick-borne infectious disease in the United States (U.S.). The ticks pick up the bacteria when they bite mice or deer that are carrying it.
It was first reported in 1977 in a town called Old Lyme, CT.
The Centers for Disease Control and Prevention (CDC) registered 25,435 confirmed cases of Lyme disease and 9,616 probable cases in 2015, an incidence of 8.9 cases in every 100,000 people.
The highest number was in Pennsylvania, with 7,351 confirmed cases. New England, the mid-Atlantic States, and the upper Midwest are most prone to ticks that can spread Lyme disease.
Fast facts on Lyme disease
- Lyme disease is the most common tick-borne disease in the U.S.
- The disease can only be passed on through the bites of certain kinds of tick.
- A common symptom of Lyme disease is an erythema migrans rash.
- Without effective treatment, symptoms disappear, but more severe symptoms can emerge weeks, months, or years later.
Initial signs and symptoms of Lyme disease are usually very mild. Some people may not notice any symptoms, or they may think they have flu.
After the initial phase, further symptoms develop. Symptoms can disappear, but the disease can affect the body in other ways, years later.
Stage 1: Early Lyme disease
Erythema migrans (EM) is a rash that often appears in the early stage of Lyme disease, from 3 to 30 days after infection or 7 days on average.
EM affects 70 to 80 percent of people who are infected.
- typically begins as a small red area that expands over several days, to reach a diameter of 12 inches or 30 centimeters
- may lose its color in the center, giving a bulls-eye appearance
- usually starts at the site of the tick bite but can appear elsewhere as the bacteria spread
- is not painful or itchy but may feel warm to the touch
The rash may be less evident on darker skin.
Stage 2: Early disseminated Lyme disease
The rash will disappear after about 4 weeks, even without treatment, but other symptoms can emerge days to months after being bitten.
- meningitis, or inflammation of the brain and spinal cord, leading to headaches and a stiff neck
- additional rashes
- fever and chills
- swollen lymph nodes
- pain in tendons, muscles, joints, and bones, especially in the large joints
- heart palpitations or irregular heartbeat
- facial palsy, or loss of muscle tone in one or both sides of the face
- dizziness and shortness of breath
- nerve pain and shooting pains, numbness or tingling in the hands or feet
These symptoms may go away without treatment within a few weeks or months, but, in time, the person may experience further complications.
Anyone who may have Lyme disease should get medical help immediately. Early treatment is more effective.