2014～2017年南京地区胃肠炎暴发中诺如病毒分子流行病学特征

Molecular Epidemiology of Norovirus Outbreaks in Nanjing,China,2014～2017

了解2014～2017年南京地区诺如病毒胃肠炎暴发流行特征、变化规律和流行株特征,为疫情控制、疫苗研发提供科学依据。收集2014年9月至2017年8月南京地区12个区疾控上送85起疑似诺如病毒急性胃肠炎暴发样本,应用荧光定量PCR和一步法RT-PCR检测诺如病毒基因序列,测序后利用分子生物学软件对序列进行分析。其中66起诺如病毒检测阳性,暴发集中于幼儿园和小学,冬春季节高发。诺如病毒优势株在连续的几个流行季持续变化,由GII.4/Sydney 2012转变为新型GII.P17-GII.17,再到GII.P16-GII.2。其中GII.P16-GII.2与全球2016～2017年参考株同源性达98.4%～99.5%。2014～2017年南京地区诺如病毒急性胃肠炎暴发的流行强度呈上升趋势。引起暴发的诺如病毒以GII为主,含多种基因型,并存在重组株,优势基因型在连续的几个流行季持续改变。诺如病毒近几年不断变异,从而逃脱人群免疫,可能是其流行趋势上升的原因之一。

The aim of this study is to investigate the epidemic characteristics,variation and predominant strains in the gastroenteritis outbreaks caused by norovirus in Nanjing,China,from 2014 to 2017 and to provide perspectives on disease prevention and vaccine development.Samples from 85 suspected norovirus outbreaks were collected from 12 district Center for Disease Control and Prevention（CDC）districts from September 2014 to August 2017.We detected the targeted norovirus gene sequences using fluorescent quantitative polymerase chain reaction（PCR）and one-step reverse transcription-polymerase chain reaction（RT-PCR）.We analyzed the sequences using bioinformatics tools.Sixty-six outbreaks were positive for norovirus,and the outbreaks mainly occurred mainly in kindergartens and primary schools in the winter and spring seasons.A shift in the predominant genotypes was evident during successive epidemic seasons,from GII.4/Sydney 2012 to the emergent GII.P17-GII.17,then to recombinant GII.P16-GII.2.The local GII.P16-GII.2 strains shared 98.4%-99.5% similarities with global reference sequences（2016-2017）.In conclusion,a rise in the prevalence of norovirus was observed since 2014.These outbreaks were caused mainly by GII,which contained multiple genotypes as well as recombinant strains,and the prevalent genotypes continued to change during successive epidemic seasons.The shift in the prevalent norovirus genotypes over time in recent years may have resulted in the escape from herd immunity,which is likely to be one of the reasons for the increase in norovirus prevalence in humans in Nanjing,China.