Genotype diversity and evolution of noroviruses GI.3[P13] associated acute gastroenteritis outbreaks in Beijing, China from 2016 to 2019.

OBJECTIVES

This study aimed to characterize the epidemiological, clinical, and genomic features of norovirus GI.3[P13] outbreaks in Beijing from 2016 to 2019.

METHODS

Stool specimens from acute gastroenteritis (AGE) outbreak cases were subjected to genotyping, whole-genome sequencing, and phylogenetic analysis.

RESULTS

From 2016 to 2019, norovirus GI.3[P13] caused 29 AGE outbreaks (452 cases) in Beijing, becoming the second most prevalent strain, followed by GII.2[P16] in 2019. Phylogenetic analysis identified three subclades, with subclade 2.2 (213 cases, 19 outbreaks) demonstrating distinct epidemiological and clinical features. This emergent subclade exhibited year-round circulation in urban/suburban areas. Multivariate analysis identified male gender (aOR = 1.79), age ≥ 13 years (aOR = 9.12), and university (aOR = 6.82) as independent risk factors. As the clinical symptom, subclade 2.2 caused more severe symptoms, including higher frequencies of vomiting (≥7 episodes/day: 18.78 % vs ≤8.67 %), diarrhea (≥7 episodes/day: 35.2 % vs ≤16.7 %), and fever (50.70 % vs ≤18.70 %). Genomic analysis revealed mutations in key structural and non-structural proteins. Bayesian analysis estimated the divergence of subclade 2.2 around mid-2017 as potential novel subgenotypes, preceding its outbreak surge in 2019.

CONCLUSIONS

Norovirus GI genotypes, like GI.3[P13], circulate continuously as sporadic and can incite outbreak surges, highlighting the necessity for improved surveillance among these genotypes.