syndrome that occurs in perhaps 20-40 percent of infections by a number of different viruses of the families Arenaviridae, Bunyaviridae, Flaviviridae, Filoviridae, etc; some types of hemorrhagic fever are tick borne, others mosquito borne, and some seem to be zoonoses; clinical manifestations are high fever, scattered petechiae, gastrointestinal tract and other organ bleeding, hypotension, and shock; kidney damage may be severe and neurologic signs may appear.