Lyme Disease
Lyme Disease, bacterial disease transmitted to people by ticks . Lyme disease is caused by a spiral-shaped bacterium known as Borrelia burgdorferi. This bacterium is frequently carried by ticks of the genus Ixodes, primarily the deer tick (also known as the black-legged tick) and the related Western black-legged tick. Immature ticks become infected by feeding on small rodents, such as the white-footed mouse, and other mammals that are infected with the bacteria. Early symptoms of Lyme disease include a red, circular, smooth rash that expands in size and may resemble a bull's-eye. The rash is painless, does not itch, and may disappear on its own. Several days to several weeks after infection, an infected person may develop flulike symptoms such as fever, headache, a stiff neck, joint and muscle pain, and severe fatigue. Doctors often treat patients early in the disease solely on the basis of their symptoms and if they have had a known or likely exposure to infected ticks. In the lat