This document describes the characteristics of viral hemorrhagic fevers.
Viral hemorrhagic fever (VHF) is an acute febrile illness characterized by malaise, prostration, generalized signs of increased vascular permeability, and abnormalities of circulatory regulation. Bleeding manifestations often occur, especially in the more severely ill patients. The viral agents that cause VHFs are all ribonucleic acid (RNA) viruses and are transmitted to humans through contact with infected animal reservoirs or arthropod vectors. The recent advent of jet travel coupled with human demographics increase the opportunity for humans to contract these infections. VHF agents are all highly infectious and cause serious diseases with high morbidity and mortality, which makes them potential biological warfare weapons. Four virus families contribute pathogens to the group of VHF agents: the Arenaviridae, Bunyaviridae, Filoviridae, and Flaviviridae. The VHF syndrome develops to varying degrees in patients infected with these viruses. The exact nature of the disease depends on viral virulence and strain characteristics, routes of exposure, dose, and host factors. Common presenting complaints are fever, myalgia, and prostration; clinical examination may reveal only conjunctival injection, mild hypotension, flushing, and petechial hemorrhages. Full-blown VHF typically evolves to shock and generalized bleeding from the mucous membranes, and often is accompanied by evidence of neurological, hematopoietic, or pulmonary involvement. VHF should be suspected in any patient presenting with a severe febrile illness and evidence of vascular involvement who has traveled to an area where the etiologic virus is known to occur, or where intelligence suggests a biological warfare threat. Patients require close supervision, and some will require intensive care. Ribavirin is an antiviral drug with efficacy for treatment of the arenaviruses and bunyaviruses. Passively administered antibody is also effective in therapy of some viral hemorrhagic fevers. The only licensed vaccine available is for yellow fever. Experimental vaccines exist for some of the viruses, but these will not be licensed in the near future. 37 references