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Recent epidemiological evidence indicates that enteric viruses are the leading cause of foodborne disease in the U.S.A. and, indeed, worldwide. Certainly, advances in epidemiology and molecular biology have improved the ability to study this previously elusive group of foodborne pathogens. The purpose of this article is to review the agents, transmission routes, epidemiology, persistence, diagnosis, and detection of foodborne viruses and their diseases, with specific reference to the role that contemporary technologies have had in improving our understanding of this important group of emerging foodborne pathogens.

Simple diagnostic tests are needed for the detection of norovirus (NoV) outbreaks. Salivary antibody assays provide an attractive alternative to collecting and testing serum or stool samples. Antibodies to Norwalk virus (NV) in oral fluid samples were compared with NV antibodies in serum collected from 38 volunteers challenged with NV inoculum. Pre-and postchallenge (day 4, 8, 14, and 21) saliva and serum samples were examined by enzyme immunoassay (EIA) using recombinant NV antigen. Of 18 infected subjects (those who shed NV in stool or who demonstrated immunoglobulin G [IgG] seroconversion), 15 (83%) had >4-fold increases in NVspecific salivary IgA and 15 (83%) had >4-fold increases in NV-specific salivary IgG when prechallenge and postchallenge saliva samples were compared. When the results of the IgA and IgG assays were combined, all 18 infected subjects showed >4-fold increases in NV-specific salivary IgG or IgA postchallenge titers compared to their prechallenge titers. One of 19 uninfected subjects had a >4-fold increase in NV-specific salivary IgG. The sensitivity of the combined assay results was 100%, and the specificity was 95%. NV-specific salivary IgA titers peaked around 14 days postchallenge. NV-specific salivary IgG and serum IgG titers continued to rise through 21 days postchallenge. The application of this EIA to an elementary school outbreak indicated that 67% of the subjects with confirmed infections had >4-fold rises in anti-NoV IgA when an antigen in the same genetic cluster as the outbreak virus was used. This is the first documented mucosal antibody response to NoV in children. This EIA provides a useful approach for diagnosing NoV outbreaks.

Bovine muscle type had a large influence on the initial activity and heat stability of triose phosphate isomerase (TPI). TPI activity in the round muscles was more heat labile than in the chuck muscles. Residual TPI activity in bovine semimembranosus muscle was determined after cooking using adequate and corresponding inadequate U.S. Department of Agriculture processing schedules. In both water bath and pilot oven studies, TPI activity was similar in adequately processed beef (about 2 U/g) and increased when inadequately processed by reducing the holding time by 0.5 and 1.0 log at each temperature. Taken together, these results suggested that TPI could be used as an endogenous time-temperature indicator to verify processing adequacy of roast beef if the muscle used in the product was known.

The objectives were to (i) compare the use of triose phosphate isomerase (TPI) activity and internal color scores for determination of cooking adequacy of beef patties and (ii) determine the effect of frozen storage and fat content on residual TPI activity in ground beef. Ground beef patties (24.4% fat) were cooked to five temperatures ranging from 60.0 to 82.2 degrees C. TPI activity decreased as beef patty cooking temperature was increased from 60.0 to 71.1 degrees C; however, no difference (P > 0.05) in activity (6.3 U/kg meat) was observed in patties cooked to 71.1 degrees C and above. Degree of doneness color scores, a* values and b* values, of ground beef patties decreased as internal temperature was increased from 60.0 to 71.1 degrees C; however, temperature had no effect on L* values. TPI activity in raw ground beef after five freeze-thaw cycles did not differ from the control. Three freeze-thaw cycles of raw ground beef resulted in a 57.2% decrease in TPI activity after cooking. TPI activity of cooked beef increased during 2 months of frozen storage, but TPI activity in ground beef stored for 3 months or longer did not differ from the unfrozen control. While past research has shown color to be a poor indicator of adequate thermal processing, our results suggest that undercooked ground beef patties could be distinguished from those that had been adequately cooked following U.S. Department of Agriculture guidelines using residual TPI activity as a marker.

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