Any of several species of the genus Mastomys. Mastomys rodents breed very frequently, produce large numbers of offspring, and are numerous in the savannas and forests of West, Central, and East Africa. Some species, like M. huberti, prefer to live in human homes.
Multimammate rats are known carriers of Lassa virus. While the exact number and type of Mastomys rodents which carry the virus is uncertain, at least two species carry Lassa virus in Sierra Leone: M. huberti and M. erythroleucus.