AN OUTBREAK OF VIRAL GASTROENTERITIS IN A NURSING-HOME - IMPORTANCE OF EXCLUDING ILL EMPLOYEES

BACKGROUND: In May 1994, 43 persons in a nursing home were reported wi th gastroenteritis. An outbreak investigation was conducted to determi ne risk factors for gastroenteritis among residents and staff. METHODS : Data were analyzed using contingency tables; relative risks (RR) and statistical significance were determined with Fisher's Exact Test. Th e chi-squared statistic to perform a goodness of fit test for the bino mial distribution was used to determine whether cases occurred randoml y and independently of each other. Stools were tested for bacterial en teric pathogens, ova, and parasites and were examined by electron micr oscopy, Southern hybridization, and reverse transcription-polymerase c hain reaction. Paired sera were collected to detect fourfold rises in antibody titer by enzyme immunoassay against Norwalk viruses. RESULTS: Of 121 residents, 62 (51%) had gastroenteritis, as did 64 (47%) of th e 136 staff. The index case was a nurse who became ill at work and con tinued to work, while symptomatic, for another 2 days. Only residents who had received medications from this nurse between May 17 and May 20 became ill on the first day of the outbreak (13 of 35 versus 0 of 5). Nurses and nurse aides were more likely than employees without direct resident contact to be cases (46 of 68 versus 18 of 58; RR, 2.18; P<. 001). Bacterial stool cultures and parasite examinations were negative . Results of electron microscopy, polymerase chain reaction with South ern hybridization, and enzyme immunoassay indicated the causative agen t was a small, round, structured virus similar to the Snow Mountain Ag ent. CONCLUSION: To minimize outbreaks in nursing homes, we recommend that ill staff be excluded from work until symptoms resolve.