The viral hemorrhagic fevers (VHFs) are a diverse group of animal and human illnesses that are caused by five distinct families of RNA viruses: the Arenaviridae, Filoviridae, Bunyaviridae, Togaviridae, and Flaviviridae. All types of VHF are characterized by fever and bleeding disorders and all can progress to high fever, shock and death in extreme cases. Some of the VHF agents cause relatively mild illnesses, such as the Scandinavian nephropathia epidemica, whilst others, such as the African Ebola virus, can cause severe, life-threatening disease.
Medical management of VHF patients may require intensive supportive care. Antiviral therapy with intravenous ribavirin may be useful in Bunyaviridae and Arenaviridae infections (specifically Lassa fever, RVF, CCHF, and HFRS due to Old World Hantavirus infection) and can be used only under an experimental protocol as a US FDA approved investigational new drug (IND). Convalescent plasma may be effective in Argentine or Bolivian hemorrhagic fevers (also available only as IND). The only licensed vaccine for a VHF is the 17D yellow fever vaccine. Experimental vaccines for other VHFs are not readily available.
Prophylactic (preventive) ribavirin may be effective for some Bunyaviridae and Arenaviridae infections (again, available only as IND).
VHF isolation guidelines dictate that all VHF patients (with the exception of dengue patients) should be cared for using strict contact precautions, including hand hygiene, double gloves, gowns, shoe and leg coverings, and faceshield or goggles. Lassa, CCHF, Ebola, and Marburg viruses may be particularly prone to nosocomial (hospital-based) spread. Airborne precautions should be utilized including, at a minimum, a fit-tested, HEPA filter-equipped respirator (such as an N-95 mask), a battery-powered, air-purifying respirator, or a positive pressure supplied air respirator to be worn by personnel coming within six feet of a VHF patient. Multiple patients should be cohorted (sequestered) to a separate building or a ward with an isolated air-handling system. Environmental decontamination is typically accomplished with hypochlorite or phenolic disinfectants.
The reasons for variation among patients infected with the same virus are unknown but stem from a complex system of virus-host interactions. Moreover, why some infected persons develop full-blown VHF while others do not also remains an unresolved issue. Virulence of the infecting agent clearly plays an important role. The “VHF syndrome” (capillary leak, bleeding diathesis and hemodynamic compromise leading to shock) occurs in a majority of patients manifesting disease from filoviruses, CCHF and the South American hemorrhagic fever viruses, while it occurs in a small minority of patients with dengue, RVF and Lassa fever.