Acute infectious disease characterized by high fever, skin eruptions, and severe headache. The classic form of typhus, caused by Rickettsia prowazekii, is transmitted from man to man by the louse Pediculus humanus corporis. A clinically similar form is caused by Rickettsia typhi and is transmitted from rat to man by the rat flea, Xenopsylla cheopis. A third type is caused by Orientia tsutsugamushi and is transmitted by the bite of an infected mite. It is limited to eastern and southeastern Asia, India, northern Australia, and the adjacent islands.