Epidemiological characteristics of norovirus infection in Lin’an District of Hangzhou City from 2012 to 2020

Objective To determine the epidemiological characteristics of norovirus infections in Lin’an District， Hangzhou City from 2012 to 2020， and provide scientific evidence for improving preventive and control measures.

Methods Descriptive epidemiological methods were used to characterize the epidemic and conduct statistical analysis to determine related factors.

Results A total of 37 clustered outbreaks of norovirus infection were reported in Lin’an District of Hangzhou from 2012 to 2020， including 8 outbreaks in kindergartens， 15 ones in elementary schools， 8 ones in middle and high schools， 2 ones in universities， and 4 other ones. The total number of cases with norovirus infection was 1 194， with the average attack rate of 3.76%. The incidence of norovirus was higher in winter and spring. It was also higher in urban areas， followed by suburban and mountainous areas neighbored to traffic lines. Moreover， attack rates differed significantly by transmission routes， including mixed contact and aerosol transmission， contact transmission， food-borne transmission， and water-borne transmission （χ²=186.91，P<0.001）. There was significant difference in the incidence among kindergartens， schools， and universities （χ²=980.15，P<0.001）. In the 37 outbreaks， norovirus were mainly classified as GⅡ in the 34 ones （accounting for 91.89%）， and GⅠ in the remaining 3 ones.

Conclusion The epidemic of norovirus infection in Lin’an District， Hangzhou City is characterized by certain population， time， space， transmission routes， and strains. It warrants enhanced health education and promotion， preparedness and response plan， syndromic surveillance， early alerting， school closure， and environmental disinfection for further prevention and control of norovirus infection.