南昌市某小学1起诺如病毒GⅡ型胃肠炎病例暴发调查

Investigation of an outbreak of Norovirus GⅡ gastroenteritis in a primary school in Nanchang

目的调查南昌市某小学1起诺如病毒GⅡ型胃肠炎暴发病例,查明此次事件发生的原因,查找可能的传播模式,提出预防控制措施。方法制定病例定义在全校师生中开展病例搜索,对病例进行回顾性队列研究,通过三间分布和卫生学调查,查找可能的致病因素。采集病例的肛拭、环境样本进行实验室检测。结果3天内共发现26例病例,全部为学生,罹患率为2.82%,涉及两个班级(混餐制);首例病例呕吐物产生的气溶胶造成班级点源传播,队列研究显示暴露于病例呕吐物3.5米内的发病风险是未暴露者的3.49倍(RR=3.49,95%CI:1.82-6.70);采集6份肛拭样本,检出5份诺如病毒GII型阳性(包括首发病例),另外2份环境样本中有1份检出诺如病毒GII型阳性。结论此起疫情为诺如病毒GⅡ型引起的学校胃肠炎暴发疫情,由首发病例呕吐物及其产生的气溶胶在密闭教室内造成大面积感染引起。

Objective To investigate an outbreak of Norovirus GⅡgastroenteritis in a primary school in Nanchang City,find out the cause of the incident,find the possible transmission mode,and put forward prevention and control measures.Methods A retrospective cohort study was conducted to search the cases among all teachers and students in the school.The possible causative factors were found by means of three spatial distribution and hygienic investigation.Anal swabs and environmental samples were collected for laboratory testing.Results A total of 26 cases were found within 3 days,all students,the incidence rate was 2.82%,involving two classes(mixed meal system);the aerosols produced by the vomit of the first case caused point-source transmission in the class.The cohort study showed that exposure to the vomit within 3.5m of the case was 3.49 times that of the unexposed(RR=3.49,95%CI:1.82-6.70).Six anal swabs were collected,five were Norovirus GII positive(including the first case),and one of the other two environmental samples was Norovirus GII positive.Conclusion The outbreak was an outbreak of gastroenteritis in schools caused by Norovirus GⅡ,and the vomit and aerosol produced by the first case caused a large area of infection in a closed classroom.