Norovirus GII.P16/GII.2 Strain in Shenzhen, China: A Retrospective Study

Abstract Background Norovirus (NoV) is the main cause of non-bacterial acute gastroenteritis (AGE) outbreaks worldwide. From September 2015 through August 2018, 203 NoV outbreaks with 2,500 patients were reported to the Shenzhen Center for Disease Control and Prevention. Methods Fecal specimens were collected from the 203 outbreaks and epidemiological data were collected through the AGE outbreak surveillance system in Shenzhen. The genotypes were determined by sequencing analysis. To gain a better understanding of evolutionary characterization of NoV in Shenzhen, the molecular evolution was analyzed by time-scale evolutionary phylogeny and amino acid mutations. Results Most of these outbreaks were associated with NoV GII.P16/GII.2 strain (45.3%,92/203) and occurred in school settings (91.6%,186/203). The timescale phylogeny suggested that the GII.P16/GII.2 strain was recombination strain and were still stable. The amino acid mutations suggested that the nonstructural proteins of the recombination strain might play a more significant role than VP1 gene in these GII.P16/GII.2 recombination strain outbreaks. Conclusions This study illustrated the characteristics of the molecular epidemiological patterns in Shenzhen, China during September 2015 to August 2018 and provided the evidence that the GII.P16/GII.2 strain was static and the epidemic trend had fade.