epidemic typhus, an acute severe rickettsial infection characterized by prolonged high fever, headache, and a dark maculopapular rash that covers most of the body. The causative organism, Rickettsia prowazekii, is transmitted indirectly as a result of the bite of the human body louse or squirrel flea or louse; the pathogen is contained in feces of the louse and enters the body tissues as the bite is scratched. Disease is manifested by the abrupt onset of an intense headache and a fever reaching 40° C (104° F) beginning after an incubation period of 1 week. The rash follows on the fifth day of onset. Complications may include vascular collapse, renal failure, pneumonia, or gangrene. Mortality rate is as high as 40% depending on preexisting clinical conditions. Treatment may include antipyretics and supportive symptomatic care. Health care workers are at risk of acquiring this infection from louse bites or louse feces. Also called classic typhus, European typhus, jail fever, louse-borne typhus. Compare murine typhus. See also Brill-Zinsser disease, Rickettsia, typhus.
