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 2010, they could not be grown in culture, and they have a very narrow host range and no suitable animal model.

[4] Establishing the viral etiology took many decades due to the difficulty of growing the virus in cell culture.

[10] These experiments demonstrated that nonbacterial, filterable agents had the capability of causing enteric disease in humans.

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.