Hemorrhagic fevers represent a wide spectrum of viral infectious diseases, out-breaking mostly as epidemics, some of them being highly lethal. They range from those caused by bunyaviridae, associated with renal or pulmonary syndromes and those recently emerging and caused by the filoviridae family of thread-like viruses. Among the latter, Ebola hemorrhagic fever (EHF) bears the highest mortality and morbidity rates. One form of the disease has been documented only in monkeys. The human form, has occurred mainly in areas surrounding rain forests in central Africa. Patients present with signs of hemorrhagic diathesis, fever, diarrhea and neurological disorders, leading sometimes to confusion with local endemic diseases. Fatal victims of the disease die of dehydration. Poor hygienic conditions facilitate the spread of the virus. Biologically, the virus seems to target both the host blood coagulative and immune defense systems. Intensive epidemiologic search have failed to establish the definitive natural host of the virus. Twice, with a 19-year interval, major outbreaks have taken place in the Democratic Republic of the Congo. The second major outbreak in the northwestern city of Kikwit in April 1995 will serve here to elucidate the mechanism of the viral infection.