广西壮族自治区梧州市某学校一起GⅡ型诺如病毒感染聚集性疫情的暴发调查

Investigation of an outbreak caused by norovirus GⅡin a school in Wuzhou,Guangxi Zhuang Autonomous Region

目的调查2021年广西壮族自治区(广西)梧州市某学校一起诺如病毒感染引起的急性胃肠炎暴发疫情,分析可能危险因素,探讨疫情处置经验,提出有针对性的防控建议。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特征,通过病例对照研究分析疫情暴发的原因,采集典型病例肛拭子、自备井水、储水池、市政末梢水、物表、留样食物等样本进行诺如病毒核酸和常见致病菌检测。结果共搜索到病例142例,罹患率为5.55%(142/2559);病例临床症状主要为呕吐(83.10%)、腹痛(83.10%)、发热(67.61%)、恶心(63.38%)、腹泻(50.70%);不同宿舍楼学生的罹患率差异有统计学意义(χ^(2)=36.978,P<0.001)。病例对照研究结果显示自备水漱口[比值比(OR)=3.78、95%置信区间(95%CI):1.736~8.234]和接触过病例(OR=2.97,95%CI:1.465~5.312)是主要危险因素,自备水漱口的频率与罹患率呈剂量反应关系(χ^(2)=14.935,P=0.002)。8份病例肛拭子、1份呕吐物、A水井、井水储水池水、井水储水罐水均检出GⅡ型诺如病毒。结论本次疫情为一起GⅡ型诺如病毒感染引起的暴发疫情,可能源于环境污染导致井水污染和人传人等多途径,自备水漱口和接触过病例是主要危险因素。缺乏相应水处理设备和未及时隔离病例是导致本次疫情规模较大的重要原因,建议加强使用自备水源的集体单位饮用水安全卫生管理,降低由水污染引起暴发疫情的风险。同时建议学校加强传染病报告管理,发现疫情及时上报和处置,防止疫情蔓延。

Objective To analyze the epidemiological characteristics of an acute gastroenteritis outbreak caused by norovirus and identify the risk factors in a school of Wuzhou,Guangxi Zhuang Autonomous Region,in 2021,evaluate the performance of the epidemic response and suggest the targeted prevention and control measures.Methods Field epidemiology survey was carried out.The clinical manifestations and the distributions of the acute gastroenteritis cases were analyzed with descriptive epidemiological method,and a case-control study was conducted to analyze the cause of this outbreak.Samples,such as anal swab,self-supplied well water,tank water,terminal water of public water supply system,object surface swab,and food sample,were collected from the typical cases for the detection of nucleic acid of norovirus and other common pathogens.Results A total of 142 acute gastroenteritis cases were reported,with an attack rate of 5.55%(142/2559).The main clinical symptoms were vomiting(83.10%),abdominal pain(83.10%),fever(67.61%),nausea(63.38%)and diarrhea(50.70%).There was a statistical difference in the attack rate among students in different dormitory buildings(χ^(2)=36.978,P<0.001).The results of the case-control study showed that gargle with self-supplied well water(OR=3.78,95%CI:1.736-8.234)and contact with acute gastroenteritis case(OR=2.97,95%CI:1.465-5.312)were the main risk factors.There was a dose-response relationship between the frequency of gargle with self-supplied well water and the attack rate(χ^(2)=14.935,P=0.002).Norovirus GⅡwas detected in 8 anal swabs,1 vomitus sample and water samples from well A and tanks.Conclusion This outbreak was caused by the infection norovirus GⅡ,possibly resulting from well water pollution in environment and human-to-human transmission.Gargle with self-supplied well water and exposure to acute gastroenteritis case were the major risk factors.The lack of appropriate water treatment equipment and the failure to isolate acute gastroenteritis cases in time were the major reasons for the spread of the epidemic.It is recommended to strengthen the hygienic management of self-supplied well water to reduce the risk of outbreaks.Otherwise,we suggest schools and child-care settings to strengthen the management of infectious disease and conduct timely reporting and response of outbreaks to prevent the spread of the epidemic.