一起学校诺如病毒感染性腹泻暴发的调查

Investigation of a outbreak of infectious diarrhea caused by Norovirus in school

目的调查与分析岳阳市平江县两所学校一起感染性腹泻暴发,并探讨病因和可能的危险因素,评价措施效果,为今后的防控提供参考。方法按照病例定义开展病例搜索,采用描述性流行病学方法进行分析,采用病例对照研究和队列研究验证假设;对学校食堂和饮用水进行卫生学调查;采集病例的肛拭子等生物样品和水源水、出厂水、学校管网末梢水等环境样品开展相关微生物检测。结果该起疫情共发病116例,A小学罹患率为10.98%（72/656）,B中学罹患率为6.96%（33/474）,另有学校附近居民病例11例;病例组直接饮用自来水的比例为78.9%,对照组直接饮用自来水的比例为36.0%（OR=6.68,95%CI=3.180~14.030）;使用该乡自来水的乡镇街道居民罹患率为2.96%（11/371）;周边不使用自来水的居民罹患率为0.33%（1/300）,两者比较差异有统计学意义（χ2=6.54,P=0.011）;检测14例病例肛拭子标本有10例诺如病毒核酸阳性,学校无二次供水,学校管网末梢水卫生学指标超标,水源水和B中学管网末梢水诺如病毒核酸弱阳性。结论此次疫情为一起诺如病毒引起的感染性腹泻暴发,发病原因为学生饮用被诺如病毒污染的自来水所致。

Objective To analyze a outbreak of infectious diarrhea in two schools in Pingjiang county of Yueyang city,soas to investigate the risk factors,and provide scientific basis for taking corresponding prevention and control measures.Methods Cases searching was performed according to the case definition,descriptive epidemiology was adopted to analyzethe distribution of the cases,case-control study and cohort study were used to validate the hypothesis,hygienic investigation wascarried out in the school cafeteria and drinking water,specimens such as anal swabs from the patients,source water,water fromfactory,terminal tap water in school were collected for microbiological detection. Results A total of 116 cases were found inthis outbreak with the attack rate of 12.33%（72/584）in primary school A and 7.22%（33/457）in middle school B,and the rest11 cases were residents near the school.The percentages of students drinking tap water in case group and control group were78.9% and 36.% respectively（OR=6.68,95%CI 3.180-14.030）.The attack rate in residents drinking the tap water in the townwas 2.96%（11/371）,and that in residents not drinking the tap water was 0.33%（1/300）,showing a statistically significantdifference（χ2=6.54,P=0.011）.Of the 14 tested anal swabs,10 were positive for norwalk viral nucleic acid.It was found that thetwo schools had no secondary water supply,and the tap water from schools didn＇t achieve the sanitary standard of drinkingwater.The source water and the terminal tap water in middle school B were positive for norwalk viral nucleic acid.Conclusion This outbreak of infectious diarrhea was caused by Norovirus which contaminated the source water and drank by the students.