Molecular epidemiological characteristics of norovirus GⅡ.2［P16］ outbreaks in a district of Beijing, 2017−2022

Objective To analyze the molecular epidemiological characteristic of norovirus epidemics caused by GⅡ.2［P16］variant in a district of Beijing and provide scientific evidence for the control of the outbreak.

Method All the samples collected from diarrhea epidemics in the district from 2017 to 2023 were detected by real-time RT-PCR for norovirus RNA, The positive samples were amplified by RT-PCR, and the gene homology and phylogenetic evolution were also used to determine the genotype, and 3 near-complete genome sequences of norovirus GⅡ.2［P16］ were obtained.

Results A total of 137 norovirus epidemics were reported in the district of Beijing from 2016 to 2019, the genotypes of norovirus were detected successfully for 83 epidemics and 35.04% of the epidemics (48/137) were caused by norovirus GⅡ.2［P16］. The annual peak of the epidemic occurred in winter and spring. The epidemics mainly occurred in child care settings and primary schools. According to the phylogenetic analysis, the 3 near-complete genomes of GⅡ.2［P16］ strains in this study belonged to the same cluster with GⅡ.2［P16］ subgroup Sub (2019−2022) in VP1 region. The RdRp region and GⅡ.2［P16］ subgroup Sub (2018−2022) belonged to the same cluster. Analysis on amino acid locus showed that 3 variation loci were found in the non-structural region of P48, including P44S, M163 T and V227I, and one variation locus (S1645C) in RdRp region.

Conclusion GⅡ.2［P16］was the main genotype of norovirus causing epidemics in the district of Beijing from January 2017 to December 2022. Continuous surveillance and genomic analysis are helpful to find the variation and emergence of the epidemic strain.