拉萨市一起水源污染引起的校园细菌性痢疾暴发调查

Outbreak investigation of a campus bacterial dysentery by water source pollution in Lhasa City

目的了解拉萨市一起学校细菌性痢疾暴发的危险因素及事件性质,为制定相应防控措施提供参考。方法采用现场流行病学调查方法,以2022年6月26日至7月1日拉萨市1所学校和1所幼儿园细菌性痢疾的疑似病例、可能病例和确诊病例为研究对象,通过询问教职工、患者,查看学校晨检记录及因病缺勤追踪记录等方式开展病例搜索。采取病例对照研究,调查可疑餐次和饮生水因素,对患者粪便、肛拭子、留样食物等行核酸片段聚合酶链反应(PCR)检测志贺菌。结果两校共搜索到55例细菌性痢疾病例,罹患率为15.41%,其中学生53例,罹患率为16.71%;教职工2例,罹患率为7.5%;流行曲线提示为点源暴露。走读生与住校生罹患率差异无统计学意义(16.10%,17.09%)(χ^(2)=0.05,P>0.05),小学生罹患率高于幼儿园学生(19.83%,6.67%)(χ^(2)=7.13,P<0.05)。病例对照显示病例组与对照组在6月24—26日间饮用生水与发病有关联(OR=4.01,95%CI=1.75~9.19,P<0.05);两校共检出23份粪便志贺菌核酸阳性,食堂门前末梢水2份,井口周围污水管中的污泥2份。结论此次事件是由管网水受污染引起的一起细菌性痢疾暴发。卫生行政部门应加大对饮用水卫生安全的监督管理力度,学校应强化供水设施管理,有效预防介水传染病的暴发。

Objective To investigate risk factors and the nature of the outbreak of bacillary dysentery in Lhasa City,so as to customize targeted prevention and control measures.Methods Using on-site epidemiological investigation,the suspected,probable and confirmed cases of bacillary dysentery in one school and one kindergarten in Lhasa City from June 26 to July 1,2022 were collected,and additional cases were identified through interview from school staffs and family members,reviewing morning examination records and tracking records of school illness-related absence.A case-control study was conducted to investigate suspicious meals and drinking raw water,and polymerase chain reaction(PCR)was performed to detect Shigella line nucleic acid fragment in the patients’feces,anal swabs,retained food,and terminal water.Results A total of 55 cases were found in two schools,with the prevalence rate of 15.41%in total and 16.71%in students(n=53),7.5%in staff(n=2).The epidemic curve was suggestive of a point source exposure.The prevalence rate among students who walk to school and students who live in the school showed no difference(16.10%,17.09%)(χ^(2)=0.05,P>0.05),and the prevalence rate was higher among elementary school students than kindergarten students(19.83%,6.67%)(χ^(2)=7.13,P<0.05).Case-control comparisons showed a direct association between drinking raw water and morbidity in the case and control groups during June 24-26(OR=4.01,95%CI=1.75-9.19,P<0.05).A total of 23 fecal Shigella nucleic acid positives were detected from the two schools,two from the end water in front of the cafeteria door,and two from sludge in the sewage pipe around the wellhead.Conclusions The outbreak of bacillary dysentery is caused by the contamination of the pipe network water.Health administrative departments should improve the supervision and management of drinking water health safety,and schools should strengthen the management of water supply facilities for effectively prevent of waterborne infectious disease outbreaks.