Viral Hemorrhagic Fevers

Viral Hemorrhagic Fevers

Barbara Knust, Pierre E. Rollin

INFECTIOUS AGENT

Viral hemorrhagic fevers (VHFs) are caused by several families of enveloped RNA viruses: filoviruses (Ebola and Marburg viruses), arenaviruses (Lassa fever, Lujo, Guanarito, Machupo, Junin, Sabia, and Chapare viruses), bunyaviruses (Rift Valley fever [RVF], Crimean-Congo hemorrhagic fever [CCHF], and hantaviruses), and flaviviruses (dengue, yellow fever, Omsk hemorrhagic fever, Kyasanur Forest disease, and Alkhurma viruses); see the Dengue and Yellow Fever sections in this chapter.

TRANSMISSION

Some VHFs are spread person to person through direct contact with symptomatic patients, body fluids, or cadavers or through inadequate infection control in a hospital setting (filoviruses, arenaviruses, CCHF virus). Zoonotic spread may occur from contact with the following:

• Livestock via slaughter or consumption of raw meat from infected animals and, potentially, unpasteurized milk (CCHF, RVF, Alkhurma viruses)
• Bushmeat, likely via slaughter or consumption of infected animals (Ebola, Marburg viruses)
• Rodents via inhalation of or contact with materials contaminated with rodent excreta (arenaviruses, hantaviruses)
• Other reservoir species, such as bats (Ebola, Marburg viruses)

Vectorborne transmission also occurs via mosquito (RVF virus) or tick (CCHF, Omsk, Kyasanur Forest disease, Alkhurma viruses) bites or by crushing infected ticks.

TREATMENT

Ribavirin is effective for treating Lassa fever and other Old World arenaviruses, New World arenaviruses, and potentially CCHF, but it is not approved by the Food and Drug Administration (FDA) for these indications. Convalescent-phase plasma is effective in treating Argentine hemorrhagic fever. Intravenous ribavirin can be obtained for compassionate use through FDA from Valeant Pharmaceuticals (Aliso Viejo, California). Requests should be initiated by the provider through FDA (301-736-3400), with simultaneous notification to Valeant (800-548-5100, extension 5 [domestic telephone] or 949-461- 6971 [international telephone]).

PREVENTION

The risk of acquiring VHF is low for international travelers. Travelers at increased risk for exposure include those engaging in animal research, health care workers, and others providing care for patients in the community, particularly where outbreaks of VHF are occurring.

Prevention should focus on avoiding contact with host or vector species in endemic countries. Travelers should not visit locations where an outbreak is occurring, avoid contact with rodents and bats, and avoid livestock in RVF- and CCHF-endemic areas. To prevent vectorborne disease, travelers should use insecticide-treated bed nets and wear insect repellent.

Standard precautions and contact and droplet precautions for suspected VHF case-patients are recommended to avoid transmission. Direct contact should be avoided with corpses of patients suspected of having died of Ebola, Marburg, or Old World arenavirus infection. Contact with or consumption of primates, bats, and other bushmeat should be avoided. Bat-inhabited caves or mines should be avoided. Investigational vaccines exist for Argentine hemorrhagic fever and RVF; however, neither is approved by FDA nor are they commonly available in the United States.

CDC website: www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/vhf.htm