2017年福州市1型登革病毒暴发疫情的调查研究

Investigation of a local dengue fever outbreak associated with serotype 1 virus in Fuzhou,2017

目的 阐明2017年福建省福州市台江区登革热(dengue ferer,DF)暴发疫情的流行病学和病原学特征,并推测传染源的来源。方法 收集病例信息并运用描述流行病学方法调查和分析该起DF暴发的流行病学特征;常规收集病例血清标本,运用双层叠帐法捕获成蚊,用于病毒核酸检测和病毒分离;采用实时荧光RT-PCR方法鉴定病毒型别,RT-PCR法扩增病毒E基因并测序,用于病毒的系统进化分析。结果 本次疫情共报告13例病例,病例均有明显的临床表现并具有高度的时空聚集性;在病例周边环境共捕获白纹伊蚊成蚊210只,媒介密度调查发现病例所在街道布雷图指数最高,而周边区域较低;分离得到4株DENV-1毒株并经实时荧光RT-PCR证实,其中3株分离自患者血清,1株分离自捕获的白纹伊蚊成蚊。4株1型登革病毒(dengue virus-1,DENV-1)的全长E基因序列完全一致。系统进化分析发现,4株DENV-1分离株与2014年越南的毒株(GenBank序列号KT825033),而非既往福建省分离株的亲缘关系最近。结论 2017年福州市DF本地暴发系由DENV-1引起,该病毒可能由福建省境外输入并经白纹伊蚊引起本地传播。

Objective To elucidate the epidemiological and etiological features of a local outbreak of dengue fever(DF)in Taijiang district in Fuzhou,Fujian province in 2017,and speculate possible viral source based on phylogenetic analysis.Methods The clinical and demographic data of cases were collected through field investigation and the outbreak was characterized epidemiologically by descriptive method.The patient′s serum were collected and the adult mosquitoes were captured by anti-mosquito double-net method for the laboratorial test and viral isolation.The viral isolates were typed by real-time fluorescent RT-PCR and their full length of viral envelope(E)genes were amplified by RT-PCR and sequenced.The E gene sequences obtained in this study,together with the reference sequences,were used for the phylogenetic analysis.Results A total of 13 cases of autochthonous DF were confirmed in the outbreak.All cases presented obvious clinical manifestations and clustered spatially and temporally.The Breteau Index(BI)of mosquito larva density was the highest in epidemic foci of Xingang street and was relatively low in surrounding areas.Four DENV-1 strains,three from patients and one from the captured adult Aedes albopictus,were isolated and identified by real-time RT-PCR.Full length E gene sequences of the four isolates were completely identical and phylogenetic analysis showed that the isolates were genetically closest to the strain(GenBank No.KT825033)from Vietnam in 2014,rather than the DENV-1 strains found in Fujian previously.Conclusions The DF outbreak occurred in Fuzhou in 2017 was caused by DENV-1 which was imported possibly from somewhere outside of Fujian province and subsequently led to local DF transmission in human via the mosquito Aedes albopictus.