Norovirus contamination in oysters

The acute gastroenteritis caused by norovirus (Genus Norovirus of the Family Caliciviridae) is the most important non-bacterial gastroenteritis in the world, and this disease is often attributable to shellfish ingestion. Numerous studies have been made in various fields of science related to medicine and food/environmental hygiene, however, few investigations have been performed from the standpoints of shellfish biology and shellfish aquaculture in Japan. Based on reports on this problem made in various fields outside the fisheries science, this paper describes briefly the features of the disease and the causative agent previously called SRSV (small round-structured virus), transmission pathway involving shellfish ingestion, contamination of the virus in oysters, and two purification methods: depuration and relaying. Finally, the importance of studies on the virus-uptake mechanism of oysters and fate of the virus in oysters is discussed in order to establish a sanitary oyster aquaculture system and effective methods of depuration and relaying.