The Japanese term kobu (kō′ bü), meaning hump or knob, was chosen to designate this genus in the family Picornaviridae because of the distinctive icosahedral structure of the viruses in this group. The genus contains the species Aichi virus and Bovine kobuvirus, and a candidate porcine kobuvirus has been identified. Aichi virus, the type species, was first recognized in 1989 as the cause of oyster-associated nonbacterial gastroenteritis in persons in the Aichi Prefecture in Japan.