Rocky Mountain Spotted Fever (RMSF) and Typhus Fever Group

(Tickborne rickettsial diseases)

Rickettsial infections are caused by a variety of bacteria, and are most often transmitted to humans by  infected fleas, lice, mites, and ticks. Rickettsial infections include Rocky mountain spotted fever, typhus fever group, anaplasmosis and ehrlichiosis.

Rocky mountain spotted fever (RMSF)

Rocky Mountain spotted fever (RMSF) belongs to the spotted fever rickettsial group of tickborne infections. RMSF disease is caused by the bacterium Rickettsia rickettsii, transmitted to humans by the bite of an infected American dog tick (Dermacentor variabilis) and other tick species. Onset of illness begins about one week after an infected tick bite. Symptoms of illness include acute onset of fever, headache, malaise, myalgia, nausea, vomiting, and rash. Severe illness may involve neurologic symptoms. Clinical laboratory findings may include thrombocytopenia, lymphopenia, leucopenia, and elevated liver enzymes. Only 13 cases were reported in Wisconsin between 2007 and 2010. Most of these infections were acquired outside of Wisconsin.

Typhus fever group (Murine typhus)

Typhus fever is a tickborne rickettsial disease caused by the bacterium Rickettsia typhi, transmitted by fleas (rodents, flying squirrels, other small mammals) and human body lice. Typhus fever cases have been reported among travelers to Asia, Africa, and southern Europe. In the United States, cases have been reported from California, Hawaii, and Texas.

Graph of Reported Rocky Mountain Spotted Fever cases by year

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Additional Info Group

Last Revised: January 2, 2018