2022年我国GII.17[P17]诺如病毒急性胃肠炎暴发流行病学特征

Epidemiological characteristics of outbreaks of norovirus GII.17[P17] acute gastroenteritis in China, 2022

目的了解我国2022年GII.17[P17]诺如病毒(Norovirus, NoV)急性胃肠炎(acute gastroenteritis, AGE)暴发的流行病学特征。方法收集2022年1~12月AGE暴发信息及标本, 应用real-time RT-PCR对样本进行NoV核酸检测, 阳性样本通过RT-PCR扩增、测序和序列分析。结果 2022年1~12月, 共报告NoV引起的AGE暴发360起, 其中266起成功获得基因分型结果, GII.17[P17]为主要基因型之一, 为34起(12.78%, 34/266), 春季检出最多(3月6起和5月7起), 主要发生在托幼机构和小学(61.76%, 21/34)。对不同年龄组感染GII.17[P17]基因型的差异进行比较发现, 5岁以下、6~18岁、19~65岁、65岁以上这四个年龄组的GII.17[P17]基因型NoV感染病例占GII基因型NoV感染病例的比例分别为11.78%(53/450)、23.52%(32/136)、52.52%(52/99)、36.36%(4/11)。本研究14株GII.17[P17]基因组在衣壳区和聚合酶区分别属于Cluster III b和Cluster III(Kawasaki308)的SC III分支, 均与引起我国2014/15季节AGE暴发流行GII.17[P17]新变异株(GZ41621株)同属一簇。与Cluster I、Cluster II和Cluster IIIa相比, Cluster IIIb存在22个氨基酸位点变化, 本研究NoV毒株所在Cluster III b主要的氨基酸变化为:抗原表位A的T294I、Q299R, 在抗原表位D发生了一个插入突变, 人组织血型抗原受体结合位点site I的H353Q。选择压力分析检测到了大量负向选择位点, 表明负向选择对VP1基因进化起着重要作用。结论 GII.17[P17]是2022年引起我国NoV AGE暴发的主要基因型之一, 本研究的GII.17[P17]毒株与引起我国2014/15季节AGE暴发流行的GII.17[P17]新变异株(GZ41621株)仍同属一簇, 在潜在表位发生少量氨基酸变异。

Objective To analyze the epidemiological characteristics of norovirus(NoV)acute gastroenteritis(AGE)outbreaks caused by GII.17[P17]variant in China,2022.Methods Information and specimens of AGE outbreaks between January and December 2022 were collected.NoV RNA was detected in all specimens by real-time RT-PCR.The viral genome of the positive specimens were amplified,sequenced and analyzed.Results Between January and December 2022,360 AGE outbreaks were reported cumulatively,of which 266 outbreaks successfully obtained genotype results.GII.17[P17]was one of the main genotypes and detected in 34 outbreaks(12.78%,34/266),with the highest number of outbreaks detected in spring(6 outbreaks in March and 7 outbreaks in May),mainly in childcare facilities and primary schools(61.76%,21/34).According to the result of NoV genotype analysis in different age groups,14 strains of GII.17[P17]in this study belonged to Cluster III b and SC III branch of Cluster III(Kawasaki308)in the capsid region and polymerase region,respectively,and both belonged to the same cluster as the variant strain(GZ41621 strain)that caused the NoV AGE outbreaks in China during the 2014/15 season.Compared to reference strains of Cluster I,Cluster II and Cluster III a,Cluster III b was provided with 22 amino acid mutations in VP1.The main amino acid changes in the subgroup of Cluster III b including the virus strains isolated in this study were at T294I and Q299R of antigen epitope A,an insertion mutation occurred at antigen epitope D,H353Q at the site I of the human histo-blood group antigen receptor binding site.The selection pressure analysis detected a large number of negative selection sites,indicating that negative selection plays an important role in the evolution of VP1 genes.Conclusions GII.17[P17]was one of the primary genotypes responsible for NoV diarrhea outbreaks in China in 2022.Phylogenetic analysis had revealed that it still belonged to the same cluster as the novel GII.17[P17]variant(strain GZ41621)that caused NoV epidemics in China during the 2014/15 season,exhibiting minor amino acid variations at the potential epitope.