The Caliciviridae are a family of "small round structured" viruses, members of Class IV of the Baltimore scheme. Caliciviridae bear resemblance to enlarged picornavirus and were formerly considered to be a genus within the Picornaviridae. They have positive-sense, single-stranded RNA which is not segmented. Thirteen species are placed in this family, divided among eleven genera. Diseases associated with this family include feline calicivirus (respiratory disease), rabbit hemorrhagic disease virus (often fatal hepatitis), and Norwalk group of viruses (gastroenteritis). Caliciviruses naturally infect vertebrates, and have been found in a number of organisms such as humans, cattle, pigs, cats, chickens, reptiles, dolphins and amphibians. The caliciviruses have a simple construction and are not enveloped. The capsid appears hexagonal/spherical and has icosahedral symmetry (T=1 or T=3
Caliciviruses are not very well studied because until 2010, they could not be grown in culture, and they have a very narrow host range and no suitable animal model. However, the application of modern genomic technologies has led to an increased understanding of the virus family.
Etymology
Calici- comes from the Latin word calix, which means "cup" or "goblet". This refers to the cup-shaped depressions on the surface of the virions of viruses in the family. The suffix -viridae is the suffix used for virus families.
Taxonomy
thumb|Phylogenetic tree of the family Caliciviridae and [[Poliovirus]]
The following genera are recognized:
- Bavovirus
- Lagovirus
- Minovirus
- Nacovirus
- Nebovirus
- Norovirus
- Recovirus
- Salovirus
- Sapovirus
- Valovirus
- Vesivirus
A number of other caliciviruses remain unclassified, including the chicken calicivirus.
Life cycle
thumb|Calicivirus genome comparison
Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment to host receptors, which mediate endocytosis. Replication follows the positive-stranded RNA virus replication model. Positive-stranded RNA virus transcription is the method of transcription. Translation takes place by leaky scanning, and RNA termination-reinitiation. Vertebrates serve as the natural host. Transmission routes are fecal-oral. These experiments demonstrated that nonbacterial, filterable agents had the capability of causing enteric disease in humans.