Objective To analyze and investigate how to select traceable samples to improve the detection rate in the epidemic situation of diarrhea caused by norovirus infection. Methods Epidemiological investigation

sample collection

and laboratory test results of an outbreak of norovirus diarrhea caused by water source pollution were analyzed. Results A total of 88 cases were found

including 51 clinically diagnosed cases and 37 laboratory-confirmed cases

with an attack rate of 26.99%（88/326）. The distribution of cases was consistent with the range of water supply

and the cases had no suspected sources of exposure

such as a history of common meals. Norovirus G Ⅱ was detected in 2 water samples

50 anal swabs/stool samples from cases

15 samples from the patient’s home environment

6 samples from the inner wall of the water source

and 2 samples from the reservoir. Norovirus G Ⅱ was detected in both anal swabs and stool samples

samples from the patient’s home environment

and samples from the water source and reservoir. Conclusion The outbreak of norovirus diarrhea caused by water source pollution has limitations in traceability detection

but the virus detection rate of environmental samples closely related to the water source remains high. Therefore

environmental samples can be adopted as sample objects for focused collection and testing.