Ebola virus disease is a severe, often fatal illness in humans. The case–fatality rate is around 50%. The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission.

The virus first appeared in 1976 in two simultaneous outbreaks, one in Sudan, and the other in Democratic Republic of Congo. The latter occurred in a village near the Ebola River, from which the disease takes its name.

The virus family Filoviridae includes three genera: Cuevavirus, Marburgvirus, and Ebolavirus. There are five species that have been identified: Zaire, Bundibugyo, Sudan, Reston and Taï Forest. The first three have been associated with large outbreaks in Africa. The virus causing the current outbreak belongs to the Zaire species.