Objective  Investigate the source of infection, transmission routes and risk factors of an outbreak of acute gastroenteritis in a factory in Suizhou City, Hubei Province in September 2021, and put forward prevention and control recommendations.

  Methods  In this study, case definitions were developed to search for cases, and then the clinical manifestations and three distribution characteristics of the cases were described. A retrospective cohort study was carried out to verify the risk factors for the outbreak. Samples from cases, water and environment were collected for the PCR detection of norovirus.

  Results  The epidemic involved Factory A and B. A total of 68 cases and 7 cases of latent infections were found. The main clinical symptoms are diarrhea and vomiting. The peak incidence of cases was from 18:00 on August 31 to 06:00 on September 1 (48 cases). The epidemic curve showed a point-source exposure pattern. The cases were mainly distributed in the second and first workshops of Factory A and Factory B. A retrospective cohort study found that compared with not eating in the canteen, having lunch in the first (RR=3.366, 95%CI: 1.321–8.577) and second (RR=10.662, 95%CI: 4.795–23.706) canteen on August 30 was a risk factor for the disease. Laboratory test results showed that 25 norovirus GⅡ positive samples were detected in 44 anal swab samples of workers; 2 norovirus GⅡ positive samples were detected in 16 anal swab samples of canteen employee; 4 norovirus positive samples were detected in 10 water samples (3 norovirus GⅡ positive and 1 norovirus G Ⅰ and Ⅱ mixed positive); 2 norovirus GⅡ positive samples were detected in 22 environmental samples.

  Conclusion  This epidemic is an outbreak caused by norovirus GⅡ infection. It is speculated that the main cause of water source pollution due to the rupture of the water pipe, and then mainly through the contamination of food supply,which is more likely to cause this outbreak. The main way of transmission is food-borne transmission, and some cases have the possibility of water-borne and human-to-human transmission. After a series of prevention and control measures such as strengthening case management, environmental disinfection and health education, the epidemic has been controlled.