The West African Ebola virus epidemic (2013–2016) was the most widespread outbreak of Ebola virus disease (EVD) in history—causing significant loss of life and social disruption in the region. The first cases were recorded in Guinea in December 2013; later, the disease spread to Liberia and Sierra Leone, with minor outbreaks occurring elsewhere. It caused significant mortality, with the case fatality rate reported at slightly above 70%, while the rate among hospitalized patients was 57–59%. Small outbreaks occurred in Nigeria and Mali, and isolated cases were recorded in Senegal, the United Kingdom and Sardinia. In addition, imported cases in the United States and Spain led to secondary infection of medical workers but did not spread further. The number of cases peaked in October 2014 and then began to decline gradually, following the commitment of substantial international resources. As of 8 May 2016, the World Health Organization (WHO) and respective governments have reported a total of 28,657 suspected cases and 11,325 deaths (39.5%), though the WHO believes that this substantially understates the magnitude of the outbreak.
On 29 March 2016, the Director-General of WHO, Dr Margaret Chan, terminated the Public Health Emergency of International Concern status of the outbreak. Although the epidemic is no longer out of control, flare-ups of the disease are likely to continue for some time.
The outbreak left about 17,000 survivors of the disease, many of whom report post-recovery symptoms termed post-Ebola syndrome, with symptoms so severe that they may require medical care for months or even years. An additional cause for concern is the apparent ability of the virus to "hide" in a recovered survivor's body for an extended period of time, only to become active months or years later – either in the same individual or in a sexual partner.