Sapovirus is a genetically diverse genus of single-stranded positive-sense RNA, non-enveloped viruses within the family Caliciviridae. Together with norovirus, sapoviruses are the most common cause of acute gastroenteritis in humans and animals. It is a monotypic taxon containing only one species, the Sapporo virus.
Natural hosts for the virus are humans and swine. The virus is transmitted through oral/fecal contact. From Wikipedia