大流行后杭州地区甲型H1N1流感病毒的流行及其支系更替特征分析

Prevalence of influenza A(H1N1)viruses in Hangzhou after 2009 pandemic and characteristics in lineage changes

目的通过分析甲型H1N1流感病毒[A(H1N1)pdm09]本地流行株的支系更替特征,了解并掌握A(H1N1)pdm09亚型流感病毒在当地的流行情况,比较历年流感疫苗与本地流行株支系的匹配程度,为本地区流感的防控策略微调提供基础数据支持。方法对2009—2020年期间A(H1N1)pdm09病毒本地流行情况进行统计分析,对随机选取的覆盖12个连续监测年度、10次流行高峰的208株代表性流行株进行血凝素基因(HA)全序列测定。通过与疫苗株和各支系参考株的序列比对,分析其基因变异情况、遗传进化和流行株支系更替特征。结果自2009年大流行以来,A(H1N1)pdm09亚型成为了本地近10年来最主要的季节性流感之一,常常与甲型H3N2、乙型流感共同流行。在2009—2020年连续12个监测年度里,由A(H1N1)pdm09亚型引起的流感流行高峰高达10次。通过HA基因序列分析发现,本地A(H1N1)pdm09亚型流行株支系来源复杂,变异切换快速。各个流行高峰的流行株与北半球当季流感疫苗推荐株相比较,常常出现因支系更替所造成遗传距离增加的现象。结论本研究提示每年更新疫苗推荐株非常必要,同时需要加强对A(H1N1)pdm09病毒流行和支系更替等特征的监测和分析,结果对指导下个流行季A(H1N1)pdm09流感病毒流行的防控具有重要参考价值。

Objective To study the epidemiological features of local influenza A(H1N1)pdm09 epidemic strains through analyzing the changes in lineages and to analyze how well the vaccine strains were matched to the circulating strains in Hangzhou.Methods Of 1112 clinical specimens from laboratory-confirmed A(H1N1)pdm09 infections in Hangzhou in consecutive seasons from 2009 to 2020,208(18.7%)with high viral load(Ct value<30)were randomly selected from 10 influenza epidemics for full-length hemagglutinin gene(HA)gene sequencing.Genetic variation,evolution and lineage changes of these representative local strains were analyzed by comparison with vaccine strains and reference strains.Results Since the 2009 pandemic,A(H1N1)pdm09 had become one of the predominant viruses causing seasonal influenza and been reported to co-circulate with influenza A(H3N2)and influenza B viruses in Hangzhou in the past decade.It caused 10 local influenza epidemics in the 12 consecutive seasons from 2009 to 2020.HA gene sequencing revealed complex sources and rapid variation of the local A(H1N1)pdm09 strains.The main epidemic strains often genetically drifted from the recommended northern hemisphere vaccine strains due to lineage changes.Conclusions This study suggested that it was essential to update the recommended vaccine strains year by year.Besides,enhanced periodic monitoring of influenza A(H1N1)pdm09 strains circulating in the region was important for the prevention and control of influenza A(H1N1)pdm09 infection in the next epidemic season.