See text The Caliciviridae are a family of "small round structured" viruses, members of Class IV of the Baltimore scheme.

[3][4] Caliciviruses naturally infect vertebrates, and have been found in a number of organisms such as humans, cattle, pigs, cats, chickens, reptiles, dolphins and amphibians.

[7] Caliciviruses are not very well studied because until recently, they could not be grown in culture, and they have a very narrow host range and no suitable animal model.

However, the recent application of modern genomic technologies has led to an increased understanding of the virus family.

[7] A recent isolate from rhesus monkeys—Tulane virus—can be grown in culture, and this system promises to increase understanding of these viruses.

Finally, in 1972, Kapikian and his colleagues isolated the Norwalk virus from volunteers using immune electron microscopy, a process that involves looking directly at antibody-antigen complexes.