Viral Haemorrhagic Fever, or EBOLA VIRUS DISEASE. A frequently fatal infection caused by a virus related to that of MARBURG DISEASE. Two large outbreaks were recorded in 1976 (one in the Sudan and one in Zaïre), with a mortality, respectively, of 50 and 80 per cent, and the disease reappeared in the Sudan in 1979 and West Africa in 2015. After an incubation period of 7–14 days, the onset is with headache of increasing severity, and fever. This is followed by diarrhoea, extensive internal bleeding and vomiting. Infection is by person-to-person contact. Serum from patients convalescing from the disease is a useful source of ANTIBODIES to the virus.