Lyme disease is an infection caused by the spiral-shaped bacteria Borrelia burgdorferi, most commonly spread by a tick bite. The disease takes its name from Lyme, Connecticut, where the illness was first identified in the United States in 1975. There are over 300,000 estimated new cases of Lyme disease in the United States each year.
The symptoms of Lyme disease depend on how long the infection has been present in the body. The first sign of Lyme disease is often an expanding round or oval red "bullseye" rash. If left untreated, people may develop neurological symptoms and heart problems, and have an approximately 60 percent chance of developing Lyme arthritis.