Lassa Fever

Abstract

Nineteen arenaviruses have been isolated in the Old and the New World, most of them identified in South or Central America. Current evidence suggests that arenaviruses have co-evolved along with their rodent hosts over a time scale of as much as 9 million years. Among six arenaviruses so far known to cause human illness, only one, Lassa virus, is from Africa. Three other arenaviruses have been isolated in Africa: Mopeia virus from Mastomys natalensis in southern Africa (Wulff et al. 1977; Johnson et al. 1981a) and two other viruses from two different rodent species, Arvicanthus and Praomys (Gonzalez et al. 1983; Swanepoel et al. 1985) in the Central African Republic. None of them has been associated with human illness (Georges et al. 1985). Lassa fever was described as a clinical entity in the 1950s, well before the Lassa virus was identified in 1969, when it was isolated from febrile American missionaries working in northern Nigeria (Frame et al. 1970; Buckley and Casals 1970). Further expansion of the family is to be anticipated with increased efforts at surveillance, including a possible a new North American arenavirus capable of causing fatal human disease.

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