Which bacterium causes Lyme disease, the tick-borne infection identified in the 1970s?

Borrelia burgdorferi causes Lyme disease, the tick-borne infection identified in the 1970s.

The bacterium is a spirochete, meaning it has a slender, spiral-shaped cell. In North America, it is mainly transmitted by Ixodes ticks, often called black-legged ticks. The infection was recognized after an unusual cluster of arthritis cases near Lyme, Connecticut, in the 1970s.

B. burgdorferi was identified by Willy Burgdorfer in 1981, and the species was later named in his honor. In Europe and parts of Asia, other Borrelia species also cause Lyme borreliosis, so B. burgdorferi is especially associated with the North American form.

Lyme disease is commonly associated with an expanding skin rash called erythema migrans, although the rash is not present in every case. It is not caused by a virus or by the bacterium responsible for Rocky Mountain spotted fever.