Viral agents of gastroenteritis: public health importance and outbreak management

Morbidity and Mortality Weekly Report, April 27, 1991

Enteroviruses

Enteroviruses cause a wide spectrum of disease, in which gastroenteritis plays a minor role (58). Although the entry of polio, coxsackie, echo, or other enteroviruses through the gut may cause incidental mild diarrheal symptoms, the spread of the virus through the bloodstream to other organs (e.g., central nervous system, heart, pleura, pancreatic islets) produces major disease manifestations. Although reports have linked some enteroviruses to illnesses in which diarrhea was the sole symptom, an outbreak or case of gastroenteritis should not be attributed to an enterovirus merely because it was isolated in the stool of an affected person.

Torovirus

Toroviruses are known causes of diarrhea among cattle, and identification in human specimens has been reported (59). Antibodies to the Breda strain of toroviruses were not present, however, in 100 human sera from Britain, and the torovirus' importance as a cause of human disease is unknown (60).

Coronavirus

Coronaviruses are well-established causes of diarrhea in animals and respiratory disease in humans. These viruses have been identified in the stool of persons with gastroenteritis (usually children <2 years of age), but human controls have been found to shed them with higher frequency (61,62), raising doubt about their etiologic role in human diarrhea. Coronaviruses have been detected most frequently in the southwest; one group reported that more than two-thirds of diarrheal stools examined by electron microscopy over an 8-year period contained such viruses, although no comparison was made with specimens from well persons (63). Worldwide, coronaviruses have been detected at highest rates in situations of poor sanitation.

METHODS OF VIRAL DETECTION

Antigen Detection

Commercial antigen-detection kits for rotavirus are widely available, inexpensive, and permit rapid viral diagnosis. Only small amounts of stool are required for the tests, and samples may be frozen before testing. Kits vary widely in range of sensitivities 70%-100%) and specificities 50%-100%) 64,65). Newborns and breast-feeding children have particularly high false-positive rates. Such kits are most useful for childhood diarrhea during the normal rotavirus season; they have less diagnostic value in situations in which rotavirus is probably rare, as in community outbreaks involving adults or in outbreaks of pediatric diarrhea outside the rotavirus season. Confirmatory testing should be performed in any case in which rotavirus disease would be unusual (e.g., among children in the summer or among adults at any time) as well as periodically to validate the reliability of the assay employed.

A commercial kit for enteric adenoviruses is also available, but because adenoviral diarrhea affects mainly children <2 years of age and because outbreaks involving adults have never been reported, the diagnostic value outside the preschool-age group is also limited.

Antigen-detection systems have been used for research on calicivirus, Norwalk, Snow Mountain agent, and astrovirus. Rapid assays for these and other agents are under development at the Viral Gastroenteritis Section, REB, DVRD, CID, CDC. Such techniques would allow the testing of large numbers of samples in a short period of time, an essential condition for determining the contribution of specific viruses to the incidence of diarrhea among populations and for identifying an etiologic agent during an outbreak.