The resurgence of the norovirus GII.4 variant associated with sporadic gastroenteritis in the post-GII.17 period in South China, 2015 to 2017

Liang Xue,Yonglai Li,Le Zhang,Qingping Wu,Juan Wang,Jumei Zhang,Haoming Wu,Weicheng Cai,Moutong Chen,Ruimin Dong,Junshan Gao

doi:10.1186/s12879-019-4331-6

Abstract

BackgroundHuman norovirus is regarded as the leading cause of nonbacterial acute diarrhea in developing and developed countries. Among all genotypes, GII.4 has been the predominant genotype, but in East Asia, it was replaced by the GII.17 in 2014/2015. However, after the prevalence of new GII.17 variant in South China, a sharply increase in the number of norovirus infections associated with sporadic acute diarrhea was detected. In this study, we would investigate the prevalence and genetic diversity of noroviruses in the sporadic acute gastroenteritis cases in the post-GII.17 period in South China.MethodsNorovirus was screened from 217 patients with sporadic acute gastroenteritis from August 2015 to October 2017 by reverse transcription-polymerase chain reaction. Then, two regions including the partial RNA polymerase and the capsid gene of positive samples were amplified and sequenced. Phylogenetic analyses were performed to determine norovirus genotypes. Complete VP1 sequences of GII.4 strains detected in this study were also amplified and subjected into evolutionary tracing analyses.ResultsA total of 43 (19.82%) norovirus samples were confirmed from 217 stool specimens, and it was found that GII.4 resurged as the new predominant variant, accounting for 76.74% (33/43) of positive samples. Only one local strain GZ2015-L550 was clustered with the contemporary GII.P16/GII.4–2012 recombinant variant, and other 32 local strains belonged to the clade with the GII.Pe/GII.4–2012 variant. Other genotypes including GII.17 (n = 4), GII.3 (n = 4), GII.8 (n = 1) and GI. 6 (n = 1) were also detected. Furthermore, all GII.4 strains were phylogenetic analyzed based on their capsid P2 subdomains. Combined with other reported 754 strains, the GII.4–2012 variant could be divided into two clades. Most GII.4 strains collected in 2016 and 2017 in this study (7/8) formed a new cluster A in Clade II with additional 103 contemporaneous strains. In addition, evolutionary tracing of the capsid P2 subdomain of this variant was also analyzed, and one specific amino acid substitutions (N373) was identified for Cluster A.ConclusionIn summary, this study confirmed a norovirus infection peak in the post-GII.17 period in South China, which was caused by the resurgence of the GII.4 variant.

Highlights

Human norovirus is regarded as the leading cause of nonbacterial acute diarrhea in developing and developed countries
Prevalence of NoVs associated with sporadic acute diarrhea in South China A total of 217 fecal specimens were collected from patients with acute diarrhea at the sentinel hospital from August 2015 to October 2017
Findings in this study suggested that the resurgence of the Genogroup II (GII).4 variant caused increased levels of NoV activity in the post GII.17 period

Summary

Introduction

Human norovirus is regarded as the leading cause of nonbacterial acute diarrhea in developing and developed countries. Norovirus (NoVs) is considered to be the main cause of non-bacterial acute gastroenteritis in developed and developing countries. This virus infects people of all ages and is responsible for almost one-fifth of all acute gastroenteritis cases worldwide [1]. This pathogen is responsible for almost half of all foodborne gastroenteritis outbreaks, and it is estimated that every year 200,000 children under 5 years old die from NoV associated gastroenteritis in developing countries [2, 3]. NoV vaccine candidates have been tested in phase 1 and phase 2 clinical trials [6, 7], but there are still no licensed virus vaccines or effective medicine treatments against NoV infections as of this writing

Methods

Results

Discussion

Conclusion