The Ebola virus is named after a river in the Democratic Republic of the Congo, (formerly Zaire) where the virus was first recognized. The Ebola virus causes an often-fatal hemorrhagic fever in humans and primates. Three of the four species of Ebola have caused disease in humans: Ebola-Zaire, Ebola-Sudan, and Ebola-Ivory Coast. Ebola-Reston causes disease in non-human primates.
Structure of the virus
Ebola is one of two members of a family of RNA viruses called the Filoviridae. Filovirus virions appear in several shapes: long, sometimes branched filaments, as well as shorter filaments shaped like a "6," a "U," or a circle. The virus filaments may measure up to 14,000 nanometers in length, with a uniform diameter of 80 nanometers. They are enveloped in a fatty membrane. Each virion contains one molecule of RNA. New viruses are created by budding from the surface of their hosts' cells; however, filovirus replication is not fully understood.
History of the virus
The first filovirus was discovered in 1967, when laboratory workers in Germany and Yugoslavia who were handling tissues from green monkeys, developed hemorrhagic fever. The virus was named after Marburg, Germany, the site of one outbreak. In 1975, Marburg reemerged in a traveler exposed in Zimbabwe became ill in Johannesburg, South Africa.
Ebola was first identified in 1976, when two outbreaks of Ebola HF occurred in Zaire and Sudan. These outbreaks were two different species of virus, named after the nations in which they were discovered. Both were highly lethal- 50% of Sudanese cases and 90% of the Zairian cases resulted in deaths.
In 1989, Ebola-Reston was discovered in an outbreak in a primate quarantine facility in the United States, but did not cause illness in infected humans. Ivory Coast was discovered in an outbreak in 1994.
Since its discovery, large outbreaks have occurred in Zaire and Sudan in 1976, again in Sudan in 1979, in Gabon in 1994, again in Zaire in 1996, and in Uganda in 2000 and 2001. All of these outbreaks resulted in fatality percentages of 50-88%.
Symptoms of Ebola hemorrhagic fever
Within a few days of infection, most patients suffer high fever, headache, muscle ache, stomach pain, fatigue, and diarrhea. Other patients may experience sore throat, hiccups, rash, red and itchy eyes, vomiting blood, and bloody diarrhea.
Within a week of infection, most patients have begun experiencing chest pain, shock, and eventually death. Other patients experience blindness and bleeding. Massive internal and external bleeding is an effect of the disease.
Medical treatment and immunization
There is no treatment for Ebola. Currently, patients receive supportive therapy. Standard therapy includes balancing the patients fluids, maintaining oxygen status and blood pressure, and treating them from complicating infections. During one outbreak, eight patients were given the blood of individuals who had been infected and recovered. Seven of the eight survived, but the small size of the sample and the young age of the patients, which predisposed them to recovery, make this inconclusive. There is currently no immunization for Ebola.
The habitat of Ebola is unknown. Researchers believe the disease is animal-borne. The virus is only known to be native to Africa. Bats and monkeys are suspected to be carriers of the disease. It seems that between outbreaks, the disease retreats into the jungles of Africa.
Spread of Ebola
Human infection is hypothesized to result from contact with an infected animal. People can be exposed to the Ebola virus through contact with the blood or secretions of an infected individual. The virus is often spread through family and friends. People can often be exposed through contact with contaminated objects, such as needles.
Transmission in health-care settings is common with Ebola. In African hospitals, patients are often cared for without use of masks, gowns, or gloves, and transmission occurs when patients are cared for without the use of these protections. Airborne transmission has been documented with Ebola-Reston in primates, but has not been documented among humans.
Centers for Disease Control. "Disease Information: Fact Sheets: Ebola Hemorrhagic Fever." (http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola.htm)
Centers for Disease Control. "Disease Information: Fact Sheets: Ebola: Case Table." (http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebotabl.htm)
Centers for Disease Control. "Disease Information: Filoviruses." (http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/filoviruses.htm)
Centers for Disease Control. "Reemergence of Ebola Virus in Africa." (http://www.cdc.gov/ncidod/EID/vol1no3/sanchez/htm)