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

Abstract In order to determine the causative pathogen and source of infection of an acute gastroenteritis outbreak in a university located in Guangzhou City, China, and summarize the lessons learned from food safety risk management.A series of epidemiological investigations were conducted in the university, including investigations of cases, food, drinking water, and the environment. A 1:4 matched case-control study was carried out to explore the risk factors for infection. Reverse transcriptase PCR was performed on all suspected cases for norovirus detection. Phylogenetic analysis was conducted to confirm pathogen typing. A total of 431 suspected cases were identified in this outbreak, of which 216 were laboratory-confirmed cases. The main clinical symptoms observed in the cases were diarrhea (62.6%) and vomiting (60.8%). A retrospective case-control study with a ratio of 1:4 was conducted. The results of multivariate analysis showed that four factors were significantly associated with the outbreak, including contact with patients' vomit or stool, presence of cases in the same dormitory, dining at Canteen B and Canteen E respectively. The odds ratios (OR) and their corresponding 95% confidence intervals (CI) for these factors were as follows: 15.587 (2.188 ~ 111.054), 3.166 (1.595 ~ 6.281), 3.86 (1.497 ~ 9.956), and 9.456(4.785 ~ 18.686), respectively. Phylogenetic analysis indicated that all eight specimens tested positive for norovirus GII.4 strains including seven confirmed outbreak cases and one food handler.Based on the environmental investigation, case-control study and laboratory test results, it was concluded that the outbreak was caused by kitchen workers infected by norovirus through contact. The health surveillance and hygiene practice of kitchen workers still need to be strengthened in the future.