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Two outbreaks of gastroenteritis in the UK which occurred nine days apart at Lymington and Southampton hospitals were investigated. The clinical and epidemiological features of both outbreaks were characteristic of small round-structured virus (SRSV) infection with rapid onset of diarrhoea and/or nausea and vomiting and propagation of the outbreaks by secondary spread. SRSV particles were observed by immune electron microscopy (EM) in 60% of faecal samples from both outbreaks and no other pathogens were detected. The index case for the second outbreak was a patient who was admitted with diarrhoea and vomiting after being discharged from Lymington hospital during the first outbreak. The possibility that the two outbreaks were caused by the same strain of SRSV was investigated by the polymerase chain reaction (PCR). New inosine-containing PCR primers were designed to amplify the RNA polymerase region of SRSV cDNA from genetic groups I and II. The PCR using the group II primers achieved a higher detection rate for SRSVs in faecal samples (68% of samples positive from both outbreaks) than immune EM. SRSVs were not detected using the group I primers or using conventional degenerate PCR primers. The nucleotide sequences of PCR amplicons from both outbreaks were identical providing molecular epidemiological evidence for the involvement of a single SRSV strain. Comparison of the RNA polymerase region of this virus with the equivalent regions of genetic group I (69.4-75.0% amino acid identify) and genetic group II (88.9-100% amino acid and 77.1-88.1% nucleotide identity) SRSVs revealed that the causative SRSV was a distinct member of genetic group II.

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SUMMARY In a small astrovirus-associated outbreak of gastroenteritis in a ward of a local children's hospital two out of five children with symptoms excreted astrovirus particles. No astrovirus particles were found in faeces from the remaining asymptomatic child, and no other viral or bacterial pathogens were found in any of the children. Virus excretion persisted for only a few days. Rising antibody titres to the astrovirus particles were demonstrated in one child, and IgM was also demonstrated in this patient's serum.In recent years one of the most successful techniques in the search for viral agents, which might cause gastroenteritis in man, has been the direct examination of faecal emulsions by electron microscopy (Kapikian et al., 1972;Flewett et al., 1973;Paver et al., 1973;Bishop et al., 1974;Caul et al., 1975;Caul and Egglestone, 1977;Appleton and Higgins, 1975; Cosgrove, 1975, 1976 Material and methodsTwo faecal specimens were collected from a child (patient T) who had been admitted to hospital with nephrotic syndrome and who subsequently developed severe gastroenteritis. These specimens were taken one day and three days after the child had diarrhoea.Routine 10y% faecal emulsions were prepared in phosphate-buffered saline (PBS), clarified by centrifugation for 30 minutes in a bench centrifuge, and concentrated for examination in the electron microscope by centrifugation for two hours at 50 OOOg in a Sorvall RC2-B ultracentrifuge. Two further specimens were collected from this child eight days and 14 days after the onset of symptoms. Twenty-five per cent faecal emulsions were prepared from these two specimens, clarified, and concentrated by centrifugation for four hours at 110 000 g in a Spinco Model 'L' ultracentrifuge.Single specimens of faeces were also collected from five other children in the same ward. One of these (patient M) had been discharged from hospital three days after patient T had diarrhoea but was readmitted three days later with an attack of vomiting. This lasted for two days and the child then developed diarrhoea which persisted for two days.A faecal specimen was collected the day before the onset of diarrhoea. Three other children also had gastrointestinal symptoms at some stage during their stay in hospital; two of these had vomiting without diarrhoea and the other (patient P) had diarrhoea and vomiting. The fifth child was asymptomatic during his stay in hospital. Twenty-five per cent emulsions were prepared from these five faecal samples and processed as described above.

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