Lyme disease is caused by bacteria (germs) that are spread by tiny, infected black-legged (deer) ticks. Both people and animals can have Lyme disease.
In the United States, Lyme disease most commonly occurs in the Northeast and mid-Atlantic regions and in the upper Midwest. In Massachusetts, Lyme disease occurs throughout the state.
Lyme disease is spread by the bite of an infected black-legged tick. The tick usually must be attached to a person for at least 24 hours before it can spread the germ. Black-legged ticks in Massachusetts can also carry the germs that cause babesiosis and human granulocytic anaplasmosis). These ticks are capable of spreading more than one type of germ in a single bite.
Lyme disease can occur during any time of the year. The bacteria that cause Lyme disease are spread by infected black-legged ticks. Young ticks (nymphs) are most active during the warm weather months between May and July. Adult ticks are most active during the fall and spring but may also be out searching for a host any time that winter temperatures are above freezing.
Symptoms of early Lyme disease, described below, usually begin to appear from 3 to 30 days after being bitten by an infected tick. If untreated, symptoms of late Lyme disease may occur from weeks to years after the initial infection.
Early stage (days to weeks): The most common early symptom is a rash (erythema migrans) where the tick was attached. It often, but not always, starts as a small red area that spreads outward, clearing up in the center so it looks like a donut. Flu-like symptoms, such as fever, headache, stiff neck, sore and aching muscles and joints, fatigue and swollen glands may also occur. Even though these symptoms may go away by themselves, without medical treatment, some people will get the rash again in other places on their bodies, and many will experience more serious problems. Treatment during the early stage prevents later, more serious problems.
Later stages (weeks to years): If untreated, people with Lyme disease can develop late-stage symptoms even if they never had a rash. The joints, nervous system and heart are most commonly affected.
People who are diagnosed with Lyme disease can be treated with antibiotics. Prompt treatment during the early stage of the disease prevents later, more serious problems.