An investigation on a food-borne outbreak caused by norovirus infection

ObjectiveTo determine the epidemiological characteristics and risk factors of a norovirus GII.17 outbreak in Minhang District of Shanghai in 2018， and provide evidence for prevention and control measures of norovirus infection.MethodsDescriptive epidemiological analysis was performed. In addition， a retrospective cohort study was conducted to determine the risk factors.ResultsFrom May 30th to June 1st of 2018， a total of 132 cases （126 clinical cases and 6 confirmed cases） were documented，with an attack rate of 29.20%（132/452）.All cases were children in a kindergarten， with the average age of 5 years and 43.9% being male. The cases were reported in all the classes， with no clustering by class or floor．The epidemic curve was characterized by a point source exposure， which was estimated to be probably between 7 AM on May 30thand 0：30 AM on May 31st. The retrospective cohort study showed that the attack rate significantly differed between the children who had taken and did not take the school lunch （RR=∞） on May