Background
The multimammate rat [Mastomys natalensis] was originally described as the reservoir for Lassa fever in West Africa. Subsequent taxonomic studies have shown that several morphologically similar animals in sub-Saharan Africa actually form a species complex. It will be years before the geographic distributions of each species can be mapped and used to interpret the restricted distribution of Lassa fever.
Incidence
Epidemics have been recognized in Nigeria, Sierra Leone and Zaire.