Non-bacterial gastroen teritis due to a number of enteri c viruses has been established s111ce
the first discoveries of Norovirus (f rmerly Norwalk virus) in 1972 and rotavirus in 1973 .
Viruses can be excreted in large numbers by infected individual s. Viruses cannot grow in or
on foods; however, they serve as vehicles for infection. Sentinent studies (Section 1. 7) have
estimated that in the United States, approximately 30.9 million (80%) of the 38.6 million
total foodborne illnesses per year can be attributed to viruses. Previously, these infections
have been grossly underestimated due to under- reporting of mild gastroenteritis and by a
lack of reliable detection methods. Fortunately, molecular biology is greatly helping in the
development of analytical procedures to analyse food and aid epidemiological studies. However, these methods have not yet evolved to the same level of application as conventional food bacteriology.