Hemorrhagic Fevers
Hemorrhagic fevers are a group of serious infections caused by certain viruses and characterized by bleeding.
Ebola and Marburg virus are two dangerous African viruses classified as filoviruses. The natural hosts (reservoir or species that maintains the virus in nature) of these viruses are not known. To date, no infections of people have occurred in the United States.
Both viruses can be transmitted from person to person by exposure to blood or infected body tissues. Person-to-person transmission occurs when family members and health care workers come into contact with blood and secretions from infected people.
Symptoms include fever, vomiting, diarrhea, bleeding, and loss of consciousness. Both infections are often fatal, with mortality varying from 25% for Marburg virus to 80 to 90% for some strains of Ebola virus.
There is no specific treatment for these infections except for general support of the person. Strict isolation precautions are necessary to prevent further spread. There is always fear that these viruses will spread from within local outbreaks to large regions, although this has not yet happened.
Lassa fever and the South American hemorrhagic fevers are infections caused by arenaviruses. These infections are transmitted from rodents to people or from person to person. Lassa fever occurs mainly in West Africa. The South American fevers are mostly confined to Bolivia and Argentina.
The infections cause fever, chest pain, diffuse body aches, and vomiting. Bleeding from the mouth, nose, stomach, and intestinal tract is common in the South American hemorrhagic fevers. Overt bleeding is less common in Lassa fever, but small spots of blood are often present under the skin. When death occurs, it is usually as a result of shock caused by diffuse leakage of fluid from blood vessels. These infections are often fatal and require strict isolation of cases to prevent transmission to health care workers and family members. There is an experimental vaccine effective against some of the South American hemorrhagic fevers. The antiviral drug ribavirin does not cure the infection but reduces the death rate.
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