In 1976, epidemics of severe hemorrhagic fever occurred simultaneously in both Zaire and Sudan. Of 550 cases reported, fatalities reached 88% in Zaire and 53% in Sudan, resulting in a total of 430 deaths. Ebola virus, named after a small river in northwest Zaire, was isolated from both epidemics. It was discovered during this outbreak that the spread of the epidemic was dependent on close contact with clinical cases and that it was stifled when basic quarantine procedures were instituted.