1起水源性诺如病毒腹泻暴发疫情的现场流行病学调查

Field epidemiological research of a water-borne norovirus diarrhea outbreak

目的探讨某工厂1起感染性腹泻暴发疫情的病原体和传播媒介及其防制对策。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,并选择罹患率最高的1个车间,采用回顾性队列研究方法,对调查对象的病例接触史、饮水习惯、就餐习惯等情况进行调查,分析可能的暴露因素。采集部分病例的粪便和肛拭子及蓄水池、直饮机、厕所洗手水等水样进行诺如病毒核酸检测。结果 2009年9月21日至10月3日,该工厂共发生病例634例,总罹患率为4.39%(634/14 439),其中男性罹患率为5.35%(411/7 677),女性罹患率为3.30%(223/6 762),男性高于女性(P<0.01)。A12栋检修科罹患率最高为21.15%(11/52),其次为A23栋总务科20.00%(4/20),第3为A15栋厨房19.57%(27/138)。回顾性队列研究共调查315人,结果显示,接触病例(RR=6.069,5%CI为3.35～10.97)和饮直饮水(RR=2.87,95%CI为1.46～5.65)是危险因素。无论是上班时还是下班时饮直饮水,直饮水饮用量与发病之间均存在剂量反应关系,饮用量越大罹患率越高(P<0.01)。共检测3份粪便1、0份肛拭子样本及13份水样,其中8份病例肛拭子样本和4份水样(2份蓄水池、1份直饮机及1份厕所洗手水的水样)中检测到诺如病毒核酸。结论该起疫情为水源性诺如病毒感染性腹泻暴发疫情。建议由市政水直接提供厂区一切生活饮用水。

Objective To probe the pathogens,transmitting vector and preventive measures for an outbreak of infectious diarrhea in a factory in Shenzhen City. Methods We screened the cases according to the case definition,analyzed the distributions of time,place and persons by descriptive epidemiology,investigated the histories of contacting the cases,the habits of drinking water and eating meals,and probe the possible exposure factors by retrospective cohort study.Then we collected some cases＇ faeces and anal swabs,and water samples from impounding reservoir,drinking fountain and washing hands＇ water in toilet for testing norovirus nucleic acid. Results From September 21 to October 3,2009,a total of 634 patients were found in the factory,with an attack rate of 4.39%（634/14 439）.The attack rate for male（5.35%） was higher than that for female（3.30%）,with statistically significant difference（P0.01）.The attack rates were the highest for persons working in the maintenance section in Building A12（21.15%）,the second for the general services section in Building A23（20.00%）,and the third for the kitchen in Building A15（19.57%）.Retrospective cohort study involved 315 persons and the results indicated contacting（RR=6.06,95%CI=3.35-10.97） and directly drinkable water（RR=2.87,95%CI=1.46-5.65） were risks.A dose-response relationship existed between the disease occurrence and water volume drunk,regardless of drinking directly potable water on duty or off duty.A total of 3 faeces specimens,10 anal swabs and 13 water samples were tested,of which 8 anal swabs and 4 water samples（2 from impounding reservoir,1 from drinking fountain and 1 from washing hands＇ water in toilet） were positive for norwalk viral nucleic acid. Conclusion It was an outbreak of water-borne norovirus infectious diarrhea.We suggest that the municipal potable water supply should be provided for the factory.