Molecular epidemiologic study on norovirus gastroenteritis outbreaks in Zhuhai from 2011 to 2016

Abstract

Objective To describe the molecular epidemiological characteristics of norovirus gastroenteritis outbreaks in Zhuhai from 2011 to 2016. Methods Anal swab specimens were collected from 576 cases with 56 outbreaks of acute norovirus gastroenteritis from 2011 to 2016. Specimens were tested by real-time RT-PCR. Three to four of norovirus positive specimens were selected from every outbreak to amplify the VP1 gene by RT-PCR and one strain was chosen randomly from every outbreaks to determine the genotype by phylogenetic tree analysis. Results Eight genotypes were identified from 56 outbreaks and all of them belonged to GⅡ genogroup. The genotype of norovirus strain changed with prevalence time. The GⅡ.4/2006b was dominant from 2011 to 2012, and replaced by GⅡ.4/Sydney _2012 during the 2012—2013 norovirus season, and both of them never appeared after Feb. 2013. GⅡ.17 was the only genotype during the 2014—2015 norovirus season. All the 7 outbreaks occurred from 2015 to 2016 were caused by GⅡ.3 norovirus. The GⅡ.17and GⅡ.3 were identified from Apr. to Sep. 2016; GⅡ.p16-GⅡ.2 were the only genotype in 12 outbreaks from Nov. to Dec. 2016. The GⅠ genogrope was never identified from 2011 to 2016 in Zhuhai. Conclusions The Norovirus GⅡ was the only pathogeny which caused the outbreaks of norovirus gastroenteritis. The recombinant norovirus strain GⅡ.p16-GⅡ.2 emerged and caused large outbreaks in the last two months of 2016 in Zhuhai; several recombinant strains of the GⅡ.p16 RdRp gene were found now, which suggests that attention should be focused on the prevalence and evolution of the recombinant norovirus. Key words: Norovirus; Outbreak; Genotype; Molecular epidemiology