Background. It is known that gastroenteritis caused by noroviruses is likely to be severe among the elderly. However, the age-specific clinical features remain unclear. We conducted an epidemiological study on foodborne norovirus outbreaks in eldercare facilities. Methods. Epidemiological and clinical information about the foodborne outbreaks which occurred between 2007 and 2011 in elder-care facilities in Tokyo was collected from the national reporting system for food-poisoning cases and the

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... vestigative reports made by the local health centers. We collected information about patients of residents and staff members, and compared symptoms by age groups classified in every 10 years old. The age-related differences in the clinical features were evaluated by the Cochran-Armitage trend test. Results. Eight foodborne norovirus outbreaks were reported during the study period. The mean attack rate was 26.6% in the residents (age range: 44-103 years) and 27.0% in the staff members (age range: 22-63 years) who took contaminated foods provided in each facility. The overall incidence of vomiting (once or more per day), diarrhea (three or more times per day) and fever (more than 37.5°C) was 65.6%, 18.3% and 18.0%, respectively. Vomiting was the most common symptom in all age groups and significantly more common in older age groups ( p = 0.0031) (figure 1). Diarrhea and fever tended to be significantly less common in older age groups ( p = 0.0014 and p = 0.0068, respectively) (figures 2 and 3).