Rocky Mountain spotted fever (RMSF) is an illness caused by Rickettsia rickettsii, a bacterial pathogen transmitted to humans through contact with ticks. Dermacentor species of ticks are most commonly associated with infection, including Dermacentor variabilis (the American dog tick) and Dermacentor andersoni (the Rocky Mountain wood tick). Disease onset averages one week following a tick bite. Age specific illness is highest for children. Illness is characterized by acute onset of fever, and may be accompanied by headache, malaise, myalgia, nausea/vomiting, or neurologic signs; a macular or maculopapular rash is reported in most patients, and a rash is often present on the palms and soles. RMSF is fatal in approximately 20% of untreated cases, and severe fulminant disease is possible.
A person with a clinically compatible illness and serologic evidence of antibody reactive with R. rickettsii in a single serum sample at a titer considered indicative of current or past infection (cutoff titers are determined by individual laboratories).
A person with a clinically compatible illness that is laboratory confirmed.