Caliciviridae

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 the calicivirus () 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) with a diameter of 35–39 nm. 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. A 2013 isolate from rhesus monkeys—Tulane virus—can be grown in culture, and this system promises to increase understanding of these viruses.