X.—The Natural History of Yellow Fever in Africa

Abstract

SynopsisThe studies on the epidemiology of yellow fever which have been carried out in Africa in the period 1925–1966 are presented in narrative form.The original isolation of the virus is described, leading on to the survey work which showed that the infection is widespread in tropical Africa and that monkeys are very important hosts—perhaps the definitive mammalian hosts—of the virus. The discoveries of a monkey-to-man cycle in which the classical vector mosquito,Aedes aegypti, is replaced byA. simpsoniand of a monkey-to-monkey cycle, in whichA. africanusis the vector, are described.Recent epidemics are discussed, particularly that in Ethiopia, where there were about 200,000 cases, with 30,000 deaths, in the period 1960–62 and where the principal vector in the man-to-man cycle wasA. simpsoni.Work on groups of animals other than monkeys is reviewed, with particular reference to studies on the lemuroid Primates of the genusGalago, which are believed to be natural hosts of the virus. It is concluded that there are still many unknown facets in the epidemiology.