2021年北京市一起小学诺如病毒感染引起的急性胃肠炎暴发疫情调查

Epidemiological investigation of an acute gastroenteritis outbreak caused by norovirus in a primary school in Beijing,2021

目的调查2021年北京市某小学一起诺如病毒感染引起的急性胃肠炎暴发疫情,分析可能的危险因素,提出有针对性的防控建议及措施,探讨疫情处置经验。方法采用现场流行病学方法开展调查,用描述性流行病学方法描述病例的临床症状和三间分布,通过病例对照研究分析疫情暴发的原因,采集病例及相关人员肛拭子和环境标本进行肠道病毒和肠道致病菌检测。结果共搜索到156例疑似病例,均为学生,罹患率为24.5%(156/638)。病例临床表现以呕吐为主(98.1%),无重症和死亡病例;流行曲线提示为点源暴露模式;病例分布具有明显的空间聚集性,不同教学楼、不同楼层、不同班级间罹患率差异均有统计学意义(P<0.001);男性罹患率为33.1%(95/352),女性罹患率为26.2%(61/286),男女性罹患率差异无统计学意义(χ^(2)=2.736,P=0.098)。病例对照研究结果显示近距离接触患者呕吐物(≤1 m)为本起疫情发生的危险因素(OR=12.14,95%CI:2.76~53.39)。57件肛拭子标本和3件环境涂抹标本检出GⅡ组诺如病毒。结论本次事件是由GⅡ组诺如病毒引起的急性胃肠炎暴发疫情,近距离暴露患病儿童呕吐物是主要的危险因素。未及时处理呕吐物和疫情迟报为本次疫情规模较大的重要原因,建议学校及时规范处置呕吐物。同时建议学校加强监测,发现疫情及时上报和处置,防止疫情蔓延。

Objective To analyze the epidemiological characteristics and identify the risk factors of an acute gastroenteritis outbreak caused by norovirus in a primary school in Beijing in 2021,suggest preventive measures and recommendations and evaluate the performance of the epidemic response.Methods Field epidemiology method were carried out.The clinical manifestations and the distribution of the cases were analyzed with descriptive epidemiological method,and a case-control study was conducted to find out the cause of this outbreak.Laboratory tests of enteroviruses and bacterial pathogens were performed by using anal swabs of the patients,food and environment samples.Results A total of 156 cases were identified,all of which were students,and the attack rate was 24.5%(156/638).The main clinical manifestations of the case were vomiting(98.1%),and no severe cases or deaths were reported.The epidemic curve suggested a point source exposure.Case distribution had obvious spatial clustering and the teaching building,floor and class specific differences in attack rate were significant(P<0.001);The attack rate was 33.1%(95/352)in boys and 26.2%(61/286)in girls,the difference was not significant(χ^(2)=2.736,P=0.098).The results of a case-control study showed that close contact with patients'vomitus(≤1 m)was associated with illness(OR=12.14,95%CI:2.76-53.39).Norovirus GⅡwas detected in 57 anal swabs and 3 environmental smear samples.Conclusion It is an outbreak of acute gastroenteritis caused by norovirus GⅡ,and close contact with vomitus was the main risk factor.Failure in disposal of vomitus in time and delayed reporting of the epidemic were important reasons for this large-scale outbreak.It is suggested for schools to timely clean off vomitus in a standardized manner,strengthen disease surveillance and reporting as well as timely epidemic response to prevent the spread of the epidemic.