Hemorrhagic Fevers and Diseases

The best-studied hemorrhagic fever is Ebola. The Ebola virus is named after a river located in the Democratic Republic of the Congo, where the virus was discovered in 1976. This outbreak occurred in the western part of the African nation of Sudan and in nearby Zaire. In 1979, another outbreak occurred in Zaire. In 1995, an outbreak that involved 316 people occurred in Kikwit, Zaire. Outbreaks have also occurred in the African regions of Gabon and the Ivory Coast.

There are four species of Ebola virus. These differ in their arrangement of their genetic material and in the severity of the infection they cause. Ebola-Zaire, Ebola-Sudan, and Ebola-Ivory Coast cause disease in humans. The fourth species, Ebola-Reston, causes disease in primates.

Ebola Reston inspired great public awareness and terror of hemorrhagic diseases. This infamous virus is named for the United States military primate research facility where the virus was isolated during a 1989 outbreak of the disease in research primates. At that time, there was fear that Ebola fever could spread to neighboring Washington, DC. Study of the cause of this outbreak determined that Ebola viruses could remain infectious after becoming dispersed in the air. Whether inhalation of the virus plays a major role in the development of the hemorrhagic fever is not clear. The current consensus is that airborne transmission is possible, but is not the principle route of infection.

Other hemorrhagic viruses can be spread by air. These include the Marburg, Lassa, Congo-Crimean, and Hantaviruses.

The Junin virus causes the hemorrhagic fever known as Argentine hemorrhagic fever. The virus was discovered in 1955, during a disease outbreak among corn harvesters in Argentina. It was later determined that the virus was spread to the workers by contact when rodent feces that had dried in the cornfields. The same route of transmission is used by the Machupo virus, which causes Bolivian hemorrhagic fever.

Congo-Crimean hemorrhagic fever is transmitted to people by ticks. The tick is likely not the natural reservoir host of the virus, but acquires the virus when it feeds on the natural reservoir host. This identity of the host is not known. This hemorrhagic fever occurs in the Crimea and in regions of Africa, Asia, and Europe.

Another hemorrhagic fever called Rift Valley fever occurs mainly in Africa. Like Ebola, it cause explosive outbreaks of disease.

Hantavirus disease was first described around the time of World War II, in Manchuria. United Nations troops stationed in Korea during the Korean War in the 1950s were sickened with the disease. A lung infection caused by the virus, which can rapidly progress to death, became prominent because of an outbreak in the southwestern region of the United States in the mid-1990s. Like some of the other hemorrhagic fevers, Hantavirus Pulmonary Syndrome is caused by inhalation of dried rodent feces.

Many of the above hemorrhagic fevers were discovered only in the past 50 to 75 years. Other hemorrhagic fevers have a longer history. For example, yellow fever was discovered in the first decade of the twentieth century, when a disease outbreak occurred among workers who were constructing the Panama Canal.

The diagnosis of hemorrhagic fevers often requires knowledge of the recent travel of the patient. This helps to clarify what natural hosts the patient may have come in contact with.