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Rocky Mountain Spotted Fever

dorsal view of a male cayenne tick, Amblyomma cajennense
A male cayenne tick, Amblyomma cajennense, a tick species which is a North, Central, and South American carrier of Rickettsia rickettsii bacteria, which cause Rocky Mountain spotted fever.
Credit: CDC

Rocky Mountain spotted fever is a tickborne disease first recognized in 1896 in the Snake River Valley of Idaho. It was originally called “black measles” because of the look of its rash in the late stages of the illness, when the skin turns black. It was a dreaded, often fatal disease, affecting hundreds of people in Idaho. By the early 1900s, the disease could be found in Washington, Montana, California, Arizona, and New Mexico.​

The Centers for Disease Control and Prevention has general information about Rocky Mountain spotted fever.


Because of the work started by Dr. Ricketts in the early 1900s, NIAID Rocky Mountain Laboratories (RML) remains a thriving center for infectious disease research on tickborne diseases, such as Lyme disease and relapsing fever. RML also continues to do research on rickettsial diseases.

Last Updated July 08, 2014