Noroviruses belong to the family of Caliciviridae, a gastrointestinal infection and the pathogens are equipped with a size 27 to 34 millionths of a millimeter smaller than four influenza viruses. Originally after the American city of Norwalk virus designated agent consists only of a protein envelope and the genome. In 1972 finally identified the virus Genogruppe GGI, GGII and GGIV are the offshoot of the human noroviruses. These are still in many different genotypes.

The noroviruses exist around the world and man is the only known carriers of the pathogen. Noroviruses are usually expressed with a gastrointestinal infection. Environmental factors have little effect on the pathogen. They survive temperatures of -20 to +60 ° Celsius and survive on food and goods.