A regional reconnaissance on yellow fever in the Sudan; with special reference to primate hosts.

Neutralization-tests with yellow fever virus performed on 666 human sera collected in the southern Sudan imply that yellow fever is still endemic south of the 10th parallel, in the south-west border of the Nuba Mountains, and in the plains west of the Nuba Mountains as far north as El Muglad. Similar tests on bloods from 110 primates revealed a high rate of immunity among both baboons (Papio sp.) (94%) and grivet monkeys (Cercopithecus aethiops) (77%), and a very low rate (1 in 56) among galagos (Galago senegalensis). It would therefore appear that, in contrast to the baboon and the grivet monkey, the galago is not significantly involved in the cycle of the virus.The epidemiological implications of these findings are discussed.