ACUTE DIARRHEA ASSOCIATED VIRUSES - AN UPDATE

Viruses recovered in stools are either cultivable viruses (enteroviruses, adenoviruses excepted type 40 and 41), or "fastidious" non cultivable viruses (rotaviruses adenoviruses 40 and 41, Norwalk, calicivirus, astrovirus, SRSV and SRV). Non cultivable viruses have been associated with many cases of diarrhea. Norwalk, two strains of calicivirus and SRV/SRSV, appear to be capable of causing outbreak. Rotavirus, astrovirus and most fastidious adenoviruses are associated with endemic spread. Specific or catch-all methods are used for diagnosis. Among the latter, electron microscopy is the most commonly used when the virus is recognizable and present in sufficient quantities. Small spherical viruses in the range 20-35 nm present greater difficulties. Polyacrylamide gel electrophoresis gives interesting epidemiological results for rotavirus. Specific methods are latex agglutination and enzyme immunoassays essentially for rotavirus and adenoviruses (all types or only 40 and 41). False positive results are few with well-designed kits. False negative results are seen in atypical strains and antigenic variants. In an outbreak, it is essential to make electron microscopic examinations. In individual cases, if no electron microscope is available, it is possible to make the diagnosis of rotavirus - and perhaps adenovirus 40 and 41 with a commercial kit. However a small number of stools contain more than one virus and they may act in synergy. In contrast many asymptomatic children may carry viruses.