Ebola virus outbreak among wild chimpanzees living in a rain forest of Cote d'Ivoire

An outbreak of Ebola in nature is described for the first time. During a few weeks in November 1994, similar to 25% of 43 members of a wild chimpanzee community disappeared or were found dead in the Tdi National Park, Cote d'Ivoire. A retrospective cohort study was done on the chimpanzee community. Laboratory procedures included histology, immunohistochemistry, bacteriology, and serology. Ebola-specific immunohistochemical staining was positive for autopsy tissue sections from 1 chimpanzee. Demographic, epidemiologic, and ecologic investigations were compatible with a point-source epidemic. Contact activities associated with a case (e.g., touching dead bodies or grooming) did not constitute significant risk factors, whereas consumption of meat did. The relative risk of meat consumption was 5.2 (95% confidence interval, 1.3-21.1), A similar outbreak occurred in November 1992 among the same community. A high mortality rate among apes tends to indicate that they are not the reservoir for the disease causing the illness. These points will have to be investigated by additional studies.