A food-borne outbreak of gastroenteritis caused by norovirus GII in a university located in Xiamen City, China

• We documented the outbreak of gastroenteritis of NoV GII caused by the food handler with asymptomatic infection.
• The food handler can return to work after three consecutive stool specimens tested negative for NoV.
• We performed sequencing in 9 positive samples to identify the infection source.
• The strains were highly homologous with EU366113|Norovirus Hu/Beijing/2006 and AB294793|Norovirus Hu/JP/2006/GII.4

SummaryObjectivesWe investigated a diarrhea outbreak that occurred at a university in China to identify the etiological agent of the outbreak, source of infection, mode of transmission, and risk factors.MethodsIn this case–control study, we compared the food sources and examined the food and water items consumed between the probable and confirmed cases and the asymptomatic control students, who were selected randomly and frequency-matched by class and age at a ratio of 1:2.ResultsOut of 7141 students (excluding teachers), 87 (1.2%) developed an illness. Thirty-three of 44 (75%) cases and 11 of 88 (13%) control students had consumed bread products supplied by an unlicensed small bakery (odds ratio 21, 95% confidence interval 8–60). Norovirus GII was detected in seven patients and in a food handler at the bread workshop and his 8-month-old son.ConclusionsThe outbreak of gastroenteritis was caused mainly by bread products contaminated with norovirus GII. A food handler with an asymptomatic norovirus GII infection was the possible source of infection.