Lyme Disease, Erythema Chronicum Migrans

Erythema chronicum migrans is the initial lesion of Lyme disease, and often appears at the site of the infecting tick bite. It is a red, enlarging rash, flat (macular) or slightly raised, and may reach from 4 to 20 inches across (the average rash is 6 inches). (Courtesy of the Centers for Disease Control.)

Lyme Disease Organism, Borrelia Burgdorferi

Borrelia burgdorferi is a spirochete similar to spirochetes of other diseases, such as relapsing fever and syphilis. This organism causes Lyme Disease. (Courtesy of the Centers for Disease Control.)

Tick, Deer Engorged on the Skin

This picture shows an engorged deer tick (Ixodes damini) embedded in the skin of a human host. In the United States, these ticks are the primary source (vector) of Lyme disease. (Courtesy of the Centers for Disease Control and M. Fergione.)

Lyme Disease - Borrelia Burgdorferi Organism

Lyme disease is caused by a bacterium known as a spirochete because of its long, corkscrew shape. The infectious organism is named Borrelia burgdorferi. The photomicrograph shows the typical corkscrew appearance of a spirochete. (Courtesy of the Centers for Disease Control.)

Tick, Deer - Adult Female

This is an adult female deer tick, Ixodes damini. It is a "vector" or insect that transmits Lyme disease to humans. (Courtesy of the Centers for Disease Control.)

Lyme Disease

Lyme disease is an acute inflammatory disease characterized by skin changes, joint inflammation and flu-like symptoms caused by the bacterium Borrelia burgdorferi transmitted by the bite of a deer tick. Symptoms resolve in 3 to 4 weeks even without treatment, but secondary or tertiary disease may develop if initial infection is not treated.