Bwamba, Bunyamwera, Germiston, Ilesha, and Tataguine viruses, all members of the family Bunyaviridae, are endemic in Africa and have never been recognized elsewhere. All these viruses can cause mild febrile illness, with or without rash; none is responsible for important epidemic disease or has a great social or economic impact. Bwamba virus was first recognized in the setting of a small outbreak in western Uganda; nine cases were confirmed by virus isolation. Bwamba infection has been recognized by virus isolation from humans in Uganda, Nigeria, Cameroon, Central African Republic, Kenya, Tanzania, and South Africa. The genomes of Bunyaviridae consist of a single strand of ribonucleic acid comprising three segments. Experimental recombination shows that genetic material can be exchanged between members of Bunyamwera group and other Bunyaviruses. Bunyamwera virus is closely related to other members of Bunyamwera group, but a prior infection by any member of this serogroup does not prevent human infection with another virus of the same group.