2017—2019年丽水市流感监测和甲型流感病毒HA基因进化分析

Surveillance on influenza and molecular evolutionary analysis of hemagglutinin gene of influenza A virus in Lishui City, 2017-2019

目的对2017—2019年丽水市流行性感冒(简称流感)监测数据和甲型流感病毒HA基因进行分析,以了解丽水市流感的流行情况、病毒亚型构成和基因进化特征。方法收集2017—2019年丽水市流感监测哨点医院的流感样病例(influenza-like illness,ILI)数据以及流感病毒病原学检测结果,采用描述性流行病学方法进行分析。将实时荧光定量方法检测阳性的标本进行MDCK细胞分离鉴定,特异性扩增H1N1、H3N2流感病毒HA基因序列,利用生物学软件比对分析。结果丽水市2017—2019年度流感样病例就诊百分比为5.70%,不同年度之间ILI%差异有统计学意义,总体阳性率为17.08%。随年龄增加流感病毒阳性检出率呈逐渐降低趋势,不同性别之间阳性率无差异。新甲型H1N1、季节性H3N2、Yamagata、Victoria均有检出,不同年份、不同年龄组各型别分布差异均有统计学意义。ILI%和流感病毒阳性检出率呈正相关(r;=0.576,P<0.05)。获得19个新甲型H1N1和27个季节性H3N2长度为1701 bp的HA全基因序列,H1N1分离株均处于2009年流感大流行后时期单一的6B.1进化分支,有14处氨基酸变异;H3N2分离株共聚类在2015年起流行的进化支3C.2a,发生了支系分化:3C.2a1和3C.2a2,有18处氨基酸变异。结论2017—2019年丽水市流感流行趋势基本平稳,符合南方地区流行特征。进化分析显示H1N1、H3N2并未发生抗原漂移,相比同期2018—2019年度疫苗株匹配性不佳,但与2020—2021年度更新后疫苗株匹配性良好。

Objective To analyze the surveillance data about influenza and hemagglutinin(HA)gene of influenza A virus in Lishui City in 2017-2019 so as to understand the epidemic situation,subtype composition and gene phylogenetic characteristics of influenza A virus in Lishui City.Methods Data regarding influenza-like illness(ILI)cases and etiological detection results of influenza virus were collected from sentinel hospitals of influenza surveillance in Lishui City from 2017 to 2019,and then analyzed by descriptive epidemiological methods.The positive specimens detected by real-time fluorescence quantitative RT-PCR were isolated by MDCK cells,and the HA gene sequences of H1 N1 and H3 N2 influenza viruses were specifically amplified and analyzed by biological software.Results The clinic visit percentage of ILI cases in Lishui City in 2017-2019 was 5.70%.ILI%in different years showed statistically significant differences,and the overall positive rate was 17.08%.The positive detection rate of influenza virus displayed a gradually decreasing trend with the increase of age,but no statistically significant difference was found in the positive rate between different genders.New A(H1 N1),seasonal H3 N2,Yamagata and Victoria were all detected,and the distribution of each type in different years and different age groups had statistically significant differences.There was a positive correlation between ILI%and the positive detection rate of influenza virus(r;=0.576,P<0.05).The completed HA gene sequences with a length of 1,701 bp were obtained from 19 new A(H1 N1)and 27 seasonal H3 N2.H1 N1 isolates all belonged to a single 6 B.1 evolutionary branch in the post-pandemic period of 2009,with 14 amino acid substitutions.H3 N2 isolates were copolymerized in 3 C.2 a which was prevalent since 2015,and differentiated into 3 C.2 a1 and 3 C.2 a2,with 18 amino acid substitutions.Conclusion The epidemic trend of influenza in Lishui City from 2017 to 2019 was basically stable,which was in line with theepidemic characteristics of the southern region.There was no antigenic drift of H1 N1 and H3 N2 by molecular evolutionary analysis,which showed poor match with the 2018-2019 vaccine strains of the same period,but good match with the 2020-2021 updatedvaccine strains.