Viral hemorrhagic fever

Abstract

Viral hemorrhagic fever (VHF) is a severe, often fatal disease in humans and nonhuman primates (e.g., monkeys and chimpanzees). The two main causes of VHF are Marburg and Ebola virus infection. Lassa fever and Crimean-Congo hemorrhagic fever occur less commonly. Marburg and Ebola viruses are RNA filoviruses. Filoviruses first emerged as the cause of significant clinical outbreaks of VHF in Marburg, Germany in 1967 and later at multiple sites in Africa in 1976. Pathogenesis appears to involve initial infection of the mononuclear phagocytic system, resulting in a generalized cytopathic effect of other cell types and eventual disruption of the coagulation system, hemorrhage, and shock. The typical fulminant disease course is attributed to an immunosuppressive effect caused by the virus. Viral transmission occurs with close, personal contact and exposure to body fluids, especially in caregivers. The risk for person-to-person transmission of VHF is highest during late-stage disease. Contact with cadavers at the time of funerals is considered an independent risk factor for exposure because of the high levels of viral antigens and particles in skin tissues. The incubation period ranges from 2 to 21 days (average 1 week). Clinical manifestations include an abrupt onset of influenza-like symptoms, sore throat, diarrhea, and abdominal pain. Other common symptoms include high fever, headaches, arthralgias, myalgias, abdominal pain, asthenia, fatigue, and hiccups. A transient morbilliform rash develops and eventually desquamates by the end of the first week of illness. Other physical findings include an exudative pharyngitis and, less commonly, conjunctivitis, jaundice, and edema. Hemorrhagic complications appear as petechiae or frank bleeding from any location, but most commonly the gastrointestinal tract. Within 1 week of infection, symptoms may progress into retrosternal pain, fulminant shock, and death. Diagnosis is based on clinical symptomatology, serologic tests, and virus isolation. Isolation must be performed in a biosafety level four facility. There is no antiviral agent or vaccine for EHF. Supportive therapy is the mainstay of treatment. Case fatality rates range from 50 to 90%.