Atlas of foodborne infections
transmitted by contaminated food and water

Atlas of Patogens Contents Information sources Glossary Administration

Other viruses transmitted via food

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Viruses


Foodborne Disease:
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Viruses transmitted via foods
There are many other groups of enteric and gastroenteritis-causing viruses, but these are reported to be associated with foods either infrequently or not at all.

 


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It is only in recent years that the role of viruses as etiological agents of food-borne illness have emerged. A recent Centers for Disease Control (CDC) report from the USA in 2000, on surveillance of food-borne disease outbreaks from 1993 to 1997, revealed that viruses accounted for 6% of all food-borne outbreaks and 8% of cases.

Hepatitis A accounted for the majority of these, followed by Norwalk-like virus (NLV). In addition, hepatitis A is the only notifiable food-borne viral disease in many countries, so it is highly likely that the incidence of food-borne illness attributed to viruses is grossly underestimated. These failures in attributing viral illness to food have mainly been due to the diagnostic difficulties in detecting viruses in an implicated food and underreporting owing to the mild nature of illness.

Food-borne viruses are generally enteric, being transmitted by the fecal-oral route. However, transmission by person-to-person contact and via contaminated water is common, as with other enteric viruses. Hepatitis A and NLV are more commonly transmitted via foods than other food-borne viruses. The most important food-borne viruses are: hepatitis A, NLV, astrovirus and rotavirus.

Astroviruses
Under the electron microscope, astroviruses appear as small, round viruses that have surface projections resembling a five- or six-pointed star (Greek astron, "star"). The illness differs from the NLV in that the incubation period is longer (3-4 days), the duration of illness is longer (often lasting for 7-14 days) and vomiting is less common, with diarrhea being the predominant symptom. In addition, the very young (<1 year) appear to be the most susceptible group, whereas NLV affect all age groups. Many astrovirus outbreaks have been reported to occur in crèches, schools, hospital wards and nursing homes, but in many cases there was no well-defined mode of transmission. One large food-borne outbreak has been reported. In Osaka, Japan, in 1991, a large outbreak of acute gastroenteritis occurred, affecting 4700 teachers and pupils from 14 schools in the city. The source was linked to contaminated food from a common supplier.

Rotaviruses
Serogroup A rotaviruses are the single most important cause of infantile gastroenteritis worldwide, affecting an estimated 130 million infants and causing 873 000 deaths every year. The rotavirus genome consists of 11 segments of double-stranded RNA surrounded by a double-shelled viral capsid. When examined by electron microscopy, the double-shelled particles resemble a wheel-like structure morphologically (Latin rota, "wheel"). The incubation period of the illness is 1-3 days, and illness is characterized by fever, vomiting and diarrhea. Although the majority of rotavirus infections involve infants, outbreaks of food-borne and water- borne disease affecting all age groups have been reported, albeit infrequently.

Picornaviruses other than hepatitis A can also be transmitted by the food-borne route. Polioviruses are transmitted by food but virulent strains of this agent are now extremely rare. Coxsackie virus and echovirus (also members of the picornavirus family) have been associated with food-borne outbreaks, but data are limited. Hepatitis E has been linked to a number of water-borne outbreaks but there has been no association with food. One food-borne outbreak of parvovirus was reported, linked to consumption of cockles.


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