An outbreak of Norovirus infection affecting an Austrian nursing home and a hospital.

On November 9, 2004, a resident in a nursing home experienced a severe episode of vomiting in the dining room, in the presence of most of the other residents and members of staff. Following that episode, 17 of the 23 (73.9%) other residents and 7 of the 18 (38.9%) staff members fell ill with diarrhea and/or vomiting in the period up to November 17. A second cluster of gastroenteritis occurred between November 11 and 28, 2004, in a nearby hospital to which eight cases among the nursing home residents had been referred. Ten of 46 (21.7%) other hospital patients and 18 of 60 (30%) members of the hospital staff suffered from vomiting or diarrhea. Epidemiological and laboratory investigations proved a causal relationship between the two institutional clusters of short-lived gastroenteritis related by time and place, and identified Norovirus genotype GGII.4 (Jamboree-like) as the causative pathogen. Control measures for Norovirus, based on epidemiological and clinical features of the outbreak, were effectively implemented in the nursing home without waiting for virological confirmation. At the hospital, specific measures were not implemented until after virological confirmation of the causative agent, by which time 16 cases had already occurred. In a suspected Norovirus outbreak it is of great importance -- especially within closed and semiclosed settings -- to implement control measures as soon as possible, even before laboratory confirmation of the agent.