Viruses.

A number of viruses have been implicated in outbreaks of viral gastroenteritis rotavirus and the Norwalk family of viruses are the leading causes.

Rotavirus:

A rotavirus has a characteristic wheel-like appearance when viewed by electron microscopy and the virus is stable in the environment. The virus has not been isolated from any food associated with an outbreak, and no satisfactory method is available for routine analysis of food.

Group A:

Endemic worldwide, the leading cause of severe diarrhoea among infants and children and accounts for about half of all cases which require hospitalisation. The number attributable to food contamination is unknown. Outbreaks of group A rotavirus diarrhoea are common among hospitalised infants, young children attending day care centres and elderly persons in nursing homes. Among adults, multiple foods served in banquets were implicated in 2 outbreaks.

Group B:

Also known as adult diarrhoea rotavirus or ADRV. Several large outbreaks of group B rotavirus involving millions of persons as a result of sewage contamination of drinking water supplies have occurred in China since 1982.

Group C:

Associated with rare and sporadic cases of diarrhoea in children in many countries. The newly recognised group C rotavirus has been implicated in rare and isolated cases of gastroenteritis. However, it was associated with 3 outbreaks among school children: one in Japan in 1989 and two in England in 1990.

Hepatitis A virus:

Hepatitis A is excreted in faeces of infected people and can produce clinical disease when susceptible individuals consume contaminated water or foods. Cold meats, sandwiches, fruits and fruit juices, milk and milk products, vegetables, salads, shellfish and iced drinks are commonly implicated in outbreaks. Water, shellfish and salads are the most frequent sources. Contamination of foods by infected workers in food processing plants and restaurants is common.

Norwalk Virus

 Norwalk virus infection is an intestinal illness that often occurs in outbreaks and is normally associated with shellfish. The viruses are passed in the stool of infected persons. People get infected by swallowing stool contaminated food or water. Contaminated water, ice, eggs, salad ingredients, and ready-to-eat foods are other sources of infection.

Anyone can get Norwalk virus infection but it may be more common in adults and older children.