Essential facts

Ebola virus disease is a severe viral haemorrhagic fever (VHF). It was first recognised in 1976, and since then there have been sporadic outbreaks in several African countries. There are five different strains, four of which have caused disease in humans. The current outbreak of the Zaire strain began in March 2014. It is the largest and most complicated ever seen, so far affecting five West African countries: Liberia, Sierra Leone, Guinea, Nigeria and Senegal. A small number of cases have occurred outside Africa, including one involving a nurse in Spain.