The Cause of Ebola
Three of the four identified subtypes of the Ebola virus are known to cause Ebola in humans. Although researchers do not know exactly how an outbreak starts, it likely begins with contact with an infected animal. From there, the virus is transmitted from human to human through direct contact with infected people or their body fluids, such as blood.
The Ebola virus was first recognized in the Democratic Republic of the Congo (formerly Zaire) in Africa, and got its name from a river there. The virus is one of two members of a family of RNA viruses called Filoviridae. There are four identified subtypes, and three of the four have caused disease in humans:
- Ebola-Ivory Coast
The fourth subtype, Ebola-Reston, has caused disease in nonhuman primates, but not in humans.
On the basis of available evidence and the nature of similar viruses, researchers believe that the virus is zoonotic (animal-borne) and is normally maintained in an animal host that is native to the African continent; however, the exact locations, origin, and natural habitat (known as the natural reservoir) remain unknown. Ebola research scientists continue to search for the exact animal host.
Ebola-Reston was isolated from infected cynomolgus monkeys that were imported from the Philippines to the United States and Italy, and is probably associated with a similar host. The Ebola virus is not known to be native to other continents, such as North America.
Ebola outbreaks typically appear sporadically. Confirmed cases of infections have been reported in:
- The Ivory Coast
- The Democratic Republic of the Congo.