分析急性胃肠炎疫情暴发的原因及危险因素。

回顾性病例对照研究分析2017年4月26日至 2017年5月5日南京市某小学出现的111例胃肠炎患者。其中男性64例，女性47例；年龄7～36岁，平均年龄(10.84±4.00)岁。通过病例对照研究探索可疑传播因素，选择一、三、五年级病例55例，按1∶1在同班级选择同性别无症状健康人群55例为对照，分析疫情发生的危险因素。采用荧光定量RT-PCR方法对人体、环境及食物标本进行诺如病毒核酸检测。

本次疫情共111例病例，其中学生108例(95.7%)，教师3例(2.6%)。实验室共检出诺如病毒GⅡ型核酸阳性11份(12.6%)，其中9份为学生肛拭子样(56%)，1份为学生粪便样(100%)，1份为三(1)班门把手涂擦样(3.33%)。病例对照研究结果显示：靠近患者呕吐物1米是危险因素(OR＝3.90，P<0.05)，说明直接或间接接触呕吐物或气溶胶是疫情发生的主要危险因素。其他因素暂未发现与该起暴发有统计学意义上的关联。

该起感染性腹泻聚集性疫情由诺如病毒引起，密切接触与暴露于患者的呕吐物是最主要的危险因素。

To identify the source and the risk factors of an acute gastroenteritis outbreak.

Retrospective case analysis was carried out on 111 gastroenteritis patients in a primary school in Nanjing from April 26, 2017 to May 5, 2017. Among them, 64 cases were males and 47 cases were females, who aged from 7 to 36, and the average age was (10.84 ± 4.00). Case-control study were used to investigate suspected transmitted factors by choosing 55 cases among first, third and fifth grade and 55 healthy asymptomatic student controls from same class and sex. TaqMan Real-Time Reverse Transcription–PCR(RT-PCR) was used for testing the specimens from the people, environment and food.

A total of 111 cases were found in this outbreak. Of which, 108 were students (95.7%), 3 cases were teachers (2.6%). Among 11 GII norovirus positive specimens(12.6%), nine were rectal swabs from student cases(56%), one was stool(100%), the other one was doorknob smear of Class One Grade Three(3.33%). The case-control study showed that the distance from patient’vomit in one meter was easy to get infected(OR=3.90, P<0.05), indicated that direct or indirect exposure to vomit or vomit aerosol was risk factor, and we did not find any statistical association between other factors and this outbreak.

The incident of an acute gastroenteritis is caused by Norwalk GII virus infection. Close contact and exposure of patients’ vomit are the major risk factors of the outbreak.