An outbreak of Norovirus GII gastroenteritis in a Chinese university: investigating transmission patterns and implications for public health interventions

On December 18, 2024, an acute gastroenteritis outbreak was reported at a university in Jinhua, China. We aimed to identify the pathogen, source, transmission routes, and risk factors to inform control strategies. A field investigation included case description by time, symptoms, and location. Case–control and retrospective cohort studies assessed dining exposures, hygiene behaviors, and illness risk. Clinical, environmental, and food-handler samples were tested by real-time RT-PCR and genotyping. From December 14 to 24, 215 cases were identified (attack rate [AR] = 0.48%), predominantly with diarrhea and vomiting. The epidemic curve suggested continuous common-source exposure then secondary transmission. Zone A had the highest AR (1.14% vs. 0.56% in B, 0.42% in C; RR = 2.71, 95% CI: 1.89–3.89 vs. Zone C). Dining at Zone A’s first-floor canteen was the primary risk factor (OR = 18.85, 95% CI: 2.44–145.39), with a dose-response association (RR = 1.82 for 2–3 meals, 3.45 for > 3 meals). Poor hand hygiene was also significant (OR = 14.60). Of 66 samples, 16 were norovirus GII-positive; 6 were canteen workers (2 asymptomatic) who worked until December 20, including the index case. Four of the 16 GII-positive samples were sequenced and all four were identified as GII.17; the genotypes of the remaining positive samples, including that of the index case, are unknown. Environmental investigation found improper glove use and inadequate tableware disinfection; four infected staff were cashiers handling takeaway packaging, likely amplifying cross-contamination. Epidemiological and laboratory evidence indicates a norovirus GII outbreak in which all four sequenced samples were identified as GII.17; foodborne transmission via infected canteen staff was strongly implicated, followed by secondary person-to-person spread. Control measures should include staff health monitoring, standardized practices, hand hygiene promotion, and prompt disinfection.