Lyme disease is a multistage, multisystem, tick-borne zoonotic infection caused by the spirochete Borrelia burgdorferi. It is the most frequently reported vector-borne infectious disease in the United States. Lyme disease is widely distributed throughout the temperate northern hemisphere, including areas of North America, Europe, and northern Asia. In the United States, it is a relatively new and emerging infectious disease that challenges epidemiologists and clinicians alike.