Epidemic typhus (also called "camp fever", "jail fever", "hospital fever", "ship fever", "famine fever", "putrid fever", "petechial fever", "Epidemic louse-borne typhus," and "louse-borne typhus") is a form of
typhus so named because the disease often causes epidemics following wars and natural disasters. The causative organism is
Rickettsia prowazekii, transmitted by the
human body louse (
Pediculus humanus humanus). Feeding on a human who carries the bacterium infects the louse.
R. prowazekii grows in the louse's gut and is excreted in its
feces. The disease is then transmitted to an uninfected human who scratches the louse bite (which itches) and rubs the feces into the wound. The
incubation period is one to two weeks.
R. prowazekii can remain viable and virulent in the dried louse feces for many days. Typhus will eventually kill the louse, though the disease will remain viable for many weeks in the dead louse.