In April 2008, several cases of acute gastroenteritis (AGE) were reported among residents and staff at a nursing home for dependent elderly individuals (Ehpad) to the health authorities in the Alpes-Maritimes department. An investigation was launched. A case of AGE was defined as diarrhea or vomiting, with or without abdominal pain or a fever exceeding 38°C. From April 18 to May 22, 2008, 66 cases of AGE were recorded. The attack rate among residents was higher than among permanent staff: 70% vs. 18%. The course of the illness was favorable without hospitalization. The norovirus strains isolated from a cook and two residents were dentate and belonged to genogroup II, Bristol genotype (GGII-4). Several criteria support the occurrence of a norovirus-induced gastroenteritis outbreak: high attack rate; occurrence of numerous cases over a short period; mild clinical presentation; short duration of illness; occurrence of cases among residents and staff members; same norovirus strain found in two residents and a cook. It is difficult to determine whether the outbreak was foodborne or due to person-to-person transmission. Several factors suggest that food played a significant role: major non-compliance issues related to poor hygiene and a flawed food preparation process; isolation of several pathogens in samples taken from a sick cook at the start of the outbreak; an attack rate of 79% at the start of the outbreak among individuals receiving blended meals; all analyzed blended meals were contaminated. This incident serves as a reminder that when cases of GEA emerge in nursing homes, rigorous hygiene measures must be implemented very quickly to limit the spread of an outbreak. (R.A.)