Rocky Mountain Spotted Fever (RMSF) and Typhus Fever Group

(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. Between 2013 and 2017, only 69 cases were reported in the state. The majority of these reported cases were acquired outside of Wisconsin.

Close up image of dog tickAn American dog tick, which can transmit RMSF.

Graph of Reported Rocky Mountain Spotted Fever cases by year

Typhus fever group (Murine typhus)

Typhus fever is a rickettsial disease caused by the bacteria Rickettsia typhi and R. prowazekii, 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.

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Additional Info Group

Last Revised: October 22, 2018