一起重庆市GⅡ.3型诺如病毒聚集性疫情的流行病学调查

Epidemiological investigation of a clustered epidemic of norovirus type GⅡ.3 in Chongqing

目的分析重庆市某学校一起诺如病毒感染性腹泻疫情的发生特点及其感染病毒的基因型别,为有效控制疫情提供科学依据,同时为类似疫情现场处置提供经验。方法运用描述性和分析性流行病学方法对疫情的流行特征和危险因素进行分析,采集病例、可能的无症状感染者、桶装水及环境有关标本,采用实时荧光定量RTPCR检测标本诺如病毒RNA,阳性标本进行逆转录PCR扩增、电泳、测序和发育树分析。结果本次疫情共有8例病例,均发生在同一班级,该班共有28名学生,班级学生罹患率28.57%,男生、女生罹患率分别为30.77%和26.67%;主要临床症状为呕吐、腹痛、腹泻,8名患病学生、4名无任何症状的该班老师、学生课桌、学生晨检牌检出诺如病毒GⅡ阳性。8株疫情病毒经序列测定和比对分析,均为GⅡ.3亚型。结论该起事件是由诺如病毒GⅡ.3感染所致的群体性事件。密切接触、无症状感染者以及共用物品可能导致此次诺如病毒的传播。

Objective To analyze the epidemiological characteristics and the genotypes of a norovirus infectious diarrhea epidemic in a school in Chongqing,explore possible transmission routes,find asymptomatic infections,and provide a scientific basis for effective control of the epidemic.MethodsCased definition,used descriptive and analytical epidemiological methods were used to analyze the epidemic characteristics and risk factors of the epidemic,collected cases,possible asymptomatic infections,bottled water and environmental samples.Real-time fluorescent quantitative RT-PCR was used to detect norovirus RNA in the specimens,and the positive specimens were subjected to reverse transcription PCR amplification,electrophoresis,sequencing,and phylogenetic tree analysis.Results There were 8 cases in this epidemic,all of which occurred in the same class.There were 28 students in the class.The attack rate was 28.57%,and the attack rates for boys and girls were 30.77%and 26.67%,respectively.The main clinical symptoms were vomiting,nausea,and abdominal pain.8 sick students,4 teachers with no symptoms,students’desks,and students’morning check-up boards were detected positive for norovirus GⅡ.The 8 strains were all of GⅡ.3 subtype after sequence determination and comparison analysis.Conclusions The incident was a mass incident caused by norovirus GⅡ.3 infection.Close contact,asymptomatic infected persons,and shared items may cause the spread of norovirus.