Lyme disease is caused by a bacterium called Borrelia burgdorferi. This bacterium
normally lives in animals such as mice, squirrels, and birds but it can be
transmitted to humans by the bite of an infected tick. In humans, the typical
symptoms of Lyme disease include fever, headache, body aches, fatigue, joint
swelling, and a characteristic skin rash called erythema migrans.
Lyme disease is the most common tick-borne disease in the United States and your risk of contacting it is directly related to your exposure to ticks. If you spend a lot of time in environments that harbor ticks such as heavily wooded or grassy areas, you should take precautions to prevent tick bites. If you do contract Lyme disease, early treatment with antibiotics usually enables complete recovery.