An outbreak of norovirus infection in a long-term-care unit in Spain

BACKGROUND: Norovirus belongs to the Caliciviridae family and causes outbreaks of infectious enteritis by fecal-oral transmission. In Spain, there have been few outbreaks reported due to this virus. We describe an outbreak on a long-term-care hospital ward. METHODS: Cases were classified as probable, confirmed, and secondary. Stool cultures were performed. Polymerase chain reaction detection of norovirus was also performed. RESULTS: The outbreak occurred from December 7 to 28, 2001, involving 60 cases (32 patients, 19 staff members, 8 patients' relatives, and 1 relative of a staff member). Most (82%) of the cases were female. The most frequently involved ages were 20 to 39 years for staff members and 70 to 89 years for patients. The incubation period of secondary cases in patients' families had a median of 48 hours (range, 1 to 7 days). Clinical symptoms included diarrhea (85%), vomiting (75%), fever (37%), nausea (23%), and abdominal pain (12%). Median duration of the disease was 48 hours (range, 1 to 7 days). All cases resolved and the outbreak halted with additional hygienic measures. Stool cultures were all negative for enteropathogenic bacteria and rotaviruses. In 16 of 23 cases, the norovirus genotype 2 antigen was detected. CONCLUSION: This outbreak of gastroenteritis due to norovirus genotype 2 affected patients, staff members, and their relatives in a long-term-care facility and was controlled in 21 days.