引起某禽类养殖场疫情的H3N2亚型流感病毒全基因组进化分析

Whole genome analysis of human H3N2 influenza virus outbreak in a poultry farm

目的了解某禽类养殖场工人间的1起流感样病例暴发疫情的流行病学特点，确定疫情性质，分析流感病毒是否存在变异或基因重组，试阐述流感病毒来源。方法采用个案调查等流行病学调查方法开展现场调查，采集所有流感样病例咽拭子标本进行核酸检测和病毒分离；对分离到的病毒进行全基因组测序，运用EditSeq和MEGA5.05软件进行序列比对和进化分析。 结果此次暴发疫情共报告流感样病例15例，罹患率为34.88%，核酸检测阳性率73.33%，分离到季节性A（H3N2）型流感病毒5株。进化分析显示分离到的H3N2流感病毒的8个基因片段均与2015—2016年流感疫苗株处于同一分支上，没有发生与禽或猪流感病毒的基因重组。5株流感病毒的血凝素（HA）有14个氨基酸位点发生了替换，其中8个位于抗原决定簇上；对神经氨酸酶基因和基质蛋白基因进行氨基酸推测分析显示，所有流感病毒均对神经氨酸酶抑制剂药物敏感，对M2离子通道抑制剂药物耐药。糖基化位点分析显示，NA新增两个糖基化位点NRT151-153、NAT245-247，其余基因未变。结论此次暴发疫情为一起季节性A（H3N2）型流感病毒暴发，病毒发生了抗原漂移，未发现与禽流感、猪流感病毒基因重组的现象。

ObjectiveTo understand the epidemiological characteristics of outbreaks and analyze the genetic characteristics of the whole genome of influenza H3N2 virus among avian-human-swine, and to elaborate the source of influenza virus.MethodsThe epidemic information was collected using the case investigation, the pharyngeal swab samples from influenza-like-illness cases were detected by real-time PCR and virus isolation. The phylogeny and molecular features of whole-genome were analyzed with EditSeq and MEGA 5.05 software.ResultsThe prevalence rate of this outbreak was 34.88%, 15 samples of throat swabs were collected, the positive rate of nucleic acid detection was 73.33%, 5 strains of seasonal influenza A （H3N2） influenza viruses were isolated. The phylogenetic analysis showed the eight gene segments of the isolated influenza viruses belonged to the same cluster with 2015-2016 influenza vaccine strain A/Switzerland/9715293/2013（H3N2）, and no recombination was found. Compared with vaccine strain, 14 variant amino acids of protein of HA were identified, and 8 of them were located in antigenic sites. All strains were sensitive to neuraminidase inhibitors while they showed resistance to blockers of M2 ion channel. The glycosylation sites analysis showed that two new glycosylation sites NRT151-153 and NAT245-247were added.ConclusionsThe outbreak was caused by seasonal influenza A （H3N2） virus which had an antigenic drift and no genetic avian-human-swine recombination was found.