Until recently, only three outbreaks of Ebola hemorrhagic fever in humans had been reported. The first two, in 1976 in Zaire and in western Sudan, were large outbreaks that resulted in more than 550 cases and 340 deaths. The third outbreak, in 1979 in Sudan, was smaller, with 34 cases and 22 deaths. In each of these outbreaks, most cases occurred in hospitals where medical supplies were inadequate and where needles and syringes were re-used. The outbreaks were quickly controlled by isolating sick patients in a place requiring the wearing of mask, gown, and gloves; sterilizing needles and syringes; and disposing of wastes and corpses in a sanitary way.

In 1995, an outbreak in Kikwit and surrounding areas in Bandundu Province, Zaire, caused 316 deaths. The outbreak was amplified in a hospital by staff who became infected through poor nursing techniques. At the request of health officials in Zaire, medical teams from CDC and the World Health Organization, and from Belgium, France, and South Africa, collaborated to investigate and control the outbreak.

Two isolated cases of Ebola hemorrhagic fever were identified in Cote d'Ivoire in 1994-1995. The most recent outbreaks were in rural Gabon in 1994 and in 1996. A patient from the 1996 Gabon outbreak traveled to Johannesburg, South Africa, and fatally infected a health-worker there as well.