广州市2017年某高校诺如病毒GⅡ.4Sydney 2012变异株感染暴发调查

Survey on a norovirus-borne outbreak caused by GⅡ.4Sydney 2012variant in a university of Guangzhou,2017

目的分析2017年广州市GⅡ.4Sydney 2012变异株引起的诺如病毒感染暴发疫情的流行特征和分子生物学特征,为诺如病毒感染疫情的防控提供依据。方法设计调查表收集病例发病资料和疫情数据,采集现症病例和厨工的肛拭子以及环境标本进行病原学检测,阳性标本进行基因测序和同源性分析。采用病例对照研究方法分析疫情的相关危险因素。结果2017年9月17—21日,广州市大学城某高校累计发生诺如病毒感染病例226例,包括223例在校学生和3例厨工,学生罹患率为0.73%(223/30711);宿舍A区学生罹患率最高(1.73%,164/9459),无院系和班级聚集性;主要危险因素为18--20日在A区食堂就餐(DR=10.75,95%CI:5.56~20.79),发病风险最高的是18日晚餐,另一危险因素是同宿舍有病例(0R=3.65,95%CI:1.92~6.94);诺如病毒核酸阳性的厨工全部来自A区食堂,阳性率为26.67%(12/45),病毒基因测序结果为GⅡ.4Sydney2012变异株,与学生病例的病毒基因序列相似度为100%。结论本次疫情是继2013年之后诺如病毒GⅡ.4Sydney 2012变异株再次在学生人群引起的较大规模暴发疫情,由食源性传播的可能性较大,同时不排除接触传播。

Objective To understand the epidemiological and molecular characteristics of a norovirus-borne outbreak caused by GⅡ.4Sydney 2012in a university of Guaugzhou to provide evidence for the prevention and control strategy on norovirus-caused epidemics.Methods A self-designed questionnaire was used to collect clinical information from the patients as well as other data related to the epidemic.Pathogen detections were performed through anal swab specimens from the patients,kitchen workers and samples from the environment.Positive samples were further sequenced for phylogenetic analysis.A case-control study was employed to identify the risk factors related to this outbreak.Results A total of 226 cases of norovirus-bome infection were identified between September 17and 21,2017,including 223students,with an attack rate of 0.73%(223/30711), and 3kitchen workers.Students staying in the A dormitory area had the highest attack rate (1.73%, 164/9459).No clustering was found in different colleges or classes.Results from the case-control study revealed that people who ate at the canteen in A dormitory area during September 18to 20 was at risk for the onset of illness (OR=10.75,95%CI:5.56-20.79).The highest risk was related to the dinner on September 18.Another significant risk factor (0R=3.65,95% CI:1.92-6.94)was close personal contact in the same room of the dorm.The 3norovirus infected kitchen workers were all from the canteen in A dormitory area where the positive rate of norovims identified in kitchen workers was26.67%(12/45).Positive samples were sequenced and sub-typed with results showing that the GⅡ.4 Sydney 2012variant and the nncleotide sequences of cases and kitchen workers were 100%identical. Conclusions The outbreak was caused by norovirus GⅡ.4Sydney 2012variant at campus.Similar outbreaks had been seen since 2013,with the routes of transmission most likely due to food-borne or oersonal contact.