Caliciviruses are non-segmented positive sense, single stranded RNA viruses that infect vertebrates including humans. The 35 to 39nm diameter capsid is hexagonal/spherical and has icosahedral symmetry.

Among the caliciviruses that are known to cause disease are:

• Genus Vesivirus - Vesicular exanthema of swine virus
• Genus Vesivirus - Feline calicivirus which causes a respiratory disease
• Genus Lagovirus - Rabbit hemorrhagic disease virus which frequently causes fatal hemorrhages
• Genus Norovirus - Norwalk virus which causes gastroenteritis in humans
• Genus Nebovirus - Newbury-1 virus which causes necrotizing hepatitis leading to fatal hemorrhages in cattle
• Genus Sapovirus - Sapporo virus  causes gastroenteritis in humans and swine. Sapoviruses usually only cause mild gastroenteritis in young children

Digitally-colorized transmission electron micrograph showing the ultrastructural morphology of Norovirus virions
CDC