Lyme disease was first described in the United States in the town of Old Lyme, Connecticut in 1975, but has now been reported in most parts of the United States. Most cases occur in the Northeast, upper Midwest, and along the Pacific coast. Mice and deer are the most commonly infected animals that serve as host to the tick. Most infections occur in the late spring, summer, and early fall. The disease can sometimes be difficult to diagnose because the symptoms may mimic other diseases. A characteristic red rash usually occurs at the site of the bite. However, the bite may go unnoticed. A few months to years after the bite, joint inflammation, neurological symptoms, and sometimes heart symptoms may occur. The initial infection is called primary Lyme disease. From there, secondary Lyme disease and tertiary Lyme disease may develop. There are more than 16,000 cases of Lyme disease per year in the United States. Risk factors for Lyme disease include walking in high grasses, other activities that increase tick exposure, and having a pet that may carry ticks home.
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