Can be fatal if not treated early.
A characteristic eschar or scab at the site of the tick bite is absent, in contrast to infections due to other tick-borne spotted fever group rickettsiae. A history of tick bite may not be elicited in up to nearly half of cases.
Signs and symptoms may be difficult to distinguish from those of common viral illnesses, leading to delayed diagnosis. Diagnosis should be considered in any person with a compatible clinical presentation and recent outdoor exposure.
Doxycycline is the drug of choice for treatment in patients of all ages and is almost always curative, especially if given in the first 5 days of illness. As the risk of death rises if appropriate therapy is not started before the fifth day of illness, doxycycline should be prescribed for suspected disease before confirmatory diagnostic test results are available.
Rocky Mountain spotted fever (RMSF) is a systemic vasculitis caused by infection with Rickettsia rickettsii , a tick-borne, gram-negative, intracellular bacterium.  Rickettsia rickettsii is one of the spotted fever group (SFG) rickettsiae and is closely related to the other group members by genetic and antigenic characteristics. It is the most frequently reported SFG rickettsial infection in North America and the most common fatal tick-borne infection in the US.    Fever, rash, headache, and vomiting are the most common clinical manifestations, but because virtually any organ may be affected the presentation and clinical course of infection may vary.     A characteristic eschar or scab at the site of the tick bite is absent, in contrast to infections due to other tick-borne SFG rickettsiae.
Detailed content on other rickettsial infections is covered by our separate Rickettsial Diseases topic.
Professor of Medicine
Section on Infectious Diseases
Wake Forest School of Medicine
CAO declares that he has no competing interests.
Professor Christopher A. Ohl would like to gratefully acknowledge Dr Steven C. Buckingham, a previous contributor to this monograph. SCB is an author of several references cited in this monograph. We were made aware that Dr Steven C. Buckingham is now deceased.
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