Methods for Detecting Viruses in Foods: Background and General Principles ¹

Viruses are sometimes transmitted through foods. Hepatitis A (HA) and some viral gastroenteritides are the diseases now known to be spread most frequently in this way, but any virus from the human intestines probably could be. Bacterial indicators of fecal contamination show limited correlation with the incidence of viruses in foods, so tests to detect the viruses themselves are needed. The epidemiologic record has led to selection of shellfish (bivalve molluscs) and vegetables and fruits as foods for which test methods should be described, and ground beef and raw milk are also considered here because of the great interest they have attracted among research workers. Viruses in foods are presently detected on the basis of the infections they cause in cultured primate cells, but these cell culture methods do not permit detection of the HA virus nor the most important of the foodborne gastroenteritis viruses. Current methods of virus detection entail liquefaction of the food sample, clarification of the sample suspension, possibly concentration of the clarified food extract, and inoculation of cell cultures; a certain amount of specialized equipment is required for some of these procedures. The inclusion of the proper controls is critical to interpretation of results that are obtained.