Caliciviruses

Caliciviral infections in humans are among the most common causes of viral-induced vomiting and diarrhoea, with illness lasting 1-4 days. Human caliciviruses (HCV) are commonly identified in faecal specimens from patients with diarrhoea. These viruses are very widely distributed worldwide and infection is very common. The most frequent source of infection appears to be contaminated food/beverages; these may cause up to 90% of food-related gastroenteritis outbreaks. Consumption of seafood is often implicated. There is strong evidence for ocean sources (reservoirs) of the viruses. For this reason, caliciviral diseases can be difficult or impossible to contain and eradicate. Pathogenic caliciviruses can be expected to continue emerging from the sea in unexpected forms at unexpected times in unexpected places.

Many caliciviruses are catholic in their choice of hosts; one type is known naturally to occur in five genera of seals, cattle, three genera of whales, donkeys, fox, and humans - and has additional susceptible hosts - paleyefish, horses, domestic swine, and primates.

Disease conditions involving calicivirus infections include blistering of the skin (particularly on the appendages and around the mouth), pneumonia, abortion, encephalitis, myocarditis, myositis, hepatitis, diarrhoea and coagulation/haemorrhage.Caliciviruses have the inherent potential and adaptive mechanisms to successfully parasitize essentially all organ systems of the many animal species that have been examined in detail.

Caliciviral infections in humans, among the most common causes of viral-induced vomiting and diarrhoea, are caused by the Norwalk and Sapporo calciviruses and the hepatitis E agent. Human caliciviruses have been resistant to in vitro cultivation, and direct study of their origins and reservoirs outside infected humans or water and foods (such as shellfish contaminated with human sewage) has been difficult. Modes of transmission, other than direct faecal-oral routes, are not well understood. In contrast, animal viruses found in ocean reservoirs, which make up a second calicivirus group, can be cultivated in vitro. These viruses can emerge and infect terrestrial hosts, including humans.