Borrelia burgdorferi transmitted by the bite of a deer tick . 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 summer. The disease is difficult to diagnose, because the symptoms mimic other diseases. A few months after the bite, muscle paralysis , joint inflammation , neurological symptoms and sometimes heart symptoms may occur. The initial infection is called primary Lyme disease .