The most widespread epidemic of Ebola virus disease in history began in 2013 and continued for over two years, resulting in significant loss of life and social disruption, mainly in three West African countries. As of 2016, although the epidemic is no longer out of control, flare-ups of the disease are likely to continue for some time.
The outbreak began in Guinea in December 2013 and then spread to Liberia and Sierra Leone, with minor outbreaks elsewhere. It has caused significant mortality, with reported case fatality rates of up to 70% and specifically 57–59% among hospitalized patients. Small outbreaks occurred in Nigeria and Mali, and isolated cases occurred in Senegal, the United Kingdom and Sardinia. Imported cases in the United States and Spain led to secondary infections of medical workers but did not spread further. As of 8 May 2016, the World Health Organization and respective governments have reported a total of 28,657 suspected cases and 11,325 deaths, though the WHO believes that this substantially understates the magnitude of the outbreak.
The WHO has warned that further small outbreaks of the disease may occur in the future, and vigilance should be maintained. A flare-up in January 2016 in Sierra Leone resulted in one death, one patient being treated, and over 100 people being quarantined. As of April 2016, the flare-up in Sierra Leone has been declared over. New flare-ups reported in Liberia are also over.