THE ROLE OF ENVIRONMENTAL CONTAMINATION WITH SMALL ROUND STRUCTURED VIRUSES IN A HOSPITAL OUTBREAK INVESTIGATED BY REVERSE-TRANSCRIPTASE POLYMERASE-CHAIN-REACTION ASSAY

In May 1994 an outbreak of vomiting and diarrhoea occurred in a 28-bed long-stay ward for the mentally infirm. The predominant symptoms were vomiting, diarrhoea, malaise and abdominal pain lasting for approxima tely 12 h in most cases. The attack rate was 62% (13/21) for patients and 46% (16/35) for staff members. Infection control measures were imp lemented (containment of infectious individuals, hand hygiene among st aff and environmental decontamination) and the ward was closed to admi ssions. Affected staff were excluded from contact with patients and th eir food until asymptomatic for 72 h. The outbreak lasted for 17 days. Faecal samples from nine symptomatic persons were negative for bacter ial enteric pathogens, Giardia, Cryptosporidium and group A rotavirus. Electron microscopy of 12 faecal samples and one sample of vomitus re vealed small round structured virus (SRSV) particles in one faecal sam ple. A further 30 faecal samples and seven vomitus samples were tested by reverse transcription polymerase chain reaction (RT-PCR) for SRSV of which 12 (40%) and 1 (14%) were positive respectively. Twenty-eight throat swabs from symptomatic and asymptomatic patients were collecte d, three (9.5%) of which were positive for SRSV by RT-PCR. Thirty-six environmental swabs were collected on the affected ward, and 11 (30%) were positive by RT-PCR. Positive swabs were from lockers, curtains an d commodes and confined to the immediate environment of symptomatic pa tients. The distribution of contamination supports the rationale of co horting sick patients.