Rocky Mountain Spotted Fever (RMSF) is the most severe and most frequently reported rickettsial illness in the United States. The disease is caused by a species of bacteria that is spread to humans by ticks. The two major sources of RMSF in the US are the American dog tick and Rocky Mountain wood tick.
Initial signs and symptoms include sudden onset of fever, headache, and muscle pain, followed by rash. The disease can be difficult to diagnose in the early stages, and without prompt treatment it can be fatal.
The name Rocky Mountain Spotted Fever is somewhat of a misnomer. Beginning in the 1930s, it became clear this disease occurred in many areas of the United States other than the Rocky Mountain region. It is broadly distributed throughout the continental United States, as well as southern Canada, Central America, Mexico, and parts of South America. Between 1981 and 1996, this disease was reported from every US state except Hawaii, Vermont, Maine, and Alaska.
RMSF remains a serious and potentially life-threatening infectious disease today. Despite the availability of effective treatment and advances in medical care, approximately 3% to 5% of individuals who become ill with RMSF will die. However, effective antibiotic therapy has dramatically reduced the number of deaths. Before the discovery of tetracycline and chloramphenichol in the late 1940s, as many as 30% of persons infected with RMSF died. For more information go to: www.cdc.gov/ncidod/dvrd/rmsf/.