Investigation of a public health emergency of acute gastroenteritis associated with norovirus contamination in centralized water supply system in a town of Beijing in 2022

Objective To investigate the infection sources and transmission routes of a public health emergency of acute gastroenteritis caused by norovirus in a town in Beijing in 2022, analyze possible risk factors, put forward targeted prevention and control suggestions.

Methods Field epidemiological survey was carried out, and descriptive epidemiological analysis was conducted to describe the distributions and clinical manifestations of the cases, Stool samples or anal swabs from the cases, external environmental samples and water samples were collected for the detection of norovirus nucleic acid. A case-control study was applied to identify risk factors.

Results A total of 324 cases were identified in 28 local communities and 6 communities in 2 factories, the attack rate was 1.82% (324/17843). The case distribution had obvious spatial clustering. The main clinical manifestations of the cases were diarrhea (99.69%), and no severe or fatal cases were reported . Case-control studies showed that the risk for the infection in those drinking unboiled water was 4.9 times higher than that in non-exposure group (OR: 4.929, 95%CI: 1.612–15.071). Norovirus was detected in 30 stool samples, 3 environmental smear samples and 12 water samples.

Conclusion This outbreak was caused by the contamination of norovirus in centralized water supplies, drinking unboiled water was a risk factor. It is suggested to strengthen surveillance for water quality, carry out regular inspections of water supply safety for the timely identification of possible contamination sources and protect public health.