Objective  To understand the genetic characteristics of norovirus GⅡ isolated from acute gastroenteritis cases in Huzhou in recent years, and provide reference for disease surveillance and prevention.

  Methods  Fluorescence quantitative RT-PCR was used to detect norovirus nucleic acid in stool samples collected from 4 acute gastroenteritis outbreak in schools and child care settings from 2013 to 2019. RT-PCR was used to amplify the norovirus RNA polymerase and capsid genes of positive samples. The genotype of norovirus was confirmed by phylogenetic analysis and online typing tools.

  Results  Four outbreaks of acute gastroenteritis occurred in December 2013, April and December 2014, and March 2019, respectively. A total of 28 samples were collected. Among the samples collected from 4 gastroenteritis outbreaks, 5, 4, 2 and 5 samples were positive for nucleic acid of norovirus GⅡ, and 1 strain from the positive samples was sequenced successfully in each outbreak. Online subtyping and phylogenetic analysis confirmed that the pathogens of the 4 outbreaks were all recombinant norovirus GⅡ.P7-GⅡ.6, but the evolutionary branches were different. The strains detected in 2013 belonged to GⅡ.P7-GⅡ.6c; the strains detected in 2014 belonged to GⅡ.P7-GⅡ.6b; the strains detected in 2019 belonged to GⅡ.P7-GⅡ.6a.

  Conclusion  Recombinant norovirus GⅡ.P7-GⅡ.6 was the pathogen causing 4 outbreaks of acute gastroenteritis in Huzhou from 2013 to 2019, and there were differences in genetic evolutionary branches among the strains isolated in different years. Given the sustainable and wide spread of norovirus GⅡ.P7-GⅡ.6 worldwide, the surveillance for this type of recombinant norovirus should be further strengthened.