一起食源性诺如病毒感染性腹泻疫情的调查

An investigation on a food-borne outbreak caused by norovirus infection

【目的】分析上海市闵行区某幼儿园一起诺如病毒感染性腹泻疫情的流行特征、流行因素,提出预防控制措施。【方法】对病例进行描述性流行病学分析,对危险因素采用回顾性队列研究。【结果】2018年5月30日—6月1日,累计发生诺如病毒感染病例132例(确诊6例,临床诊断126例),罹患率为29.20%(132/452)。病例皆为幼儿,年龄中位数为5岁,男童占43.9%;疫情波及幼儿园的所有班级,无班级和楼层聚集性;流行曲线提示点源暴露,可能暴露时间为5月30日7:00—5月31日0:30。回顾性队列研究显示,进食与未进食5月30日幼儿园供应的午餐(RR=∞)、进食与未进食海鲜面疙瘩(RR=6.19,95%CI:0.92~41.6)幼儿的罹患率差异有统计学意义(P<0.05)。共采集73件标本,其中6名病例和1名无症状厨师丙的标本检出诺如病毒GII.17型阳性,1件海鲜面疙瘩剩余食品标本检出嗜水气单胞菌阳性;厨师丙的无症状排毒期>30 d。【结论】此次疫情为食用幼儿园被诺如病毒污染的海鲜面疙瘩所致,应加强集体单位食堂食品卫生操作规范管理,定期监测餐饮从业人员诺如病毒携带情况。

[Objective]To determine the epidemiological characteristics and risk factors of a norovirus GII.17 outbreak in Minhang District of Shanghai in 2018,and provide evidence for prevention and control measures of norovirus infection.[Methods]Descriptive epidemiological analysis was performed. In addition,a retrospective cohort study was conducted to determine the risk factors.[Results]From May 30;to June 1;of 2018,a total of 132 cases(126 clinical cases and 6 confirmed cases)were documented,with an attack rate of 29.20%(132/452).All cases were children in a kindergarten,with the average age of 5 years and 43.9% being male. The cases were reported in all the classes,with no clustering by class or floor.The epidemic curve was characterized by a point source exposure,which was estimated to be probably between 7 AM on May 30;and 0:30 AM on May 31;. The retrospective cohort study showed that the attack rate significantly differed between the children who had taken and did not take the school lunch(RR=∞)on May 30;,and those who had taken and did not take seafood noodles(RR=4.11,95%CI:1.09-15.55)(P<0.05). Among a total of 73 specimens,six specimens collected in child cases and one specimen in an asymptomatic chef tested positive for GII.17 type of norovirus. In addition,one retained food specimen of seafood noodles was positive for Aeromonas hydrophila. Viral shedding in the asymptomatic chef remained over 30 days.[Conclusion]The outbreak was caused by seafood noodles contaminated by norovirus. It warrants enhancement in the regulation of food safety in canteens and regular examination of norovirus infection in catering industry employees.