浙江省一起由桶装水所致的诺如病毒胃肠炎暴发调查

A norovirus-borne outbreak caused by contaminated bottled spring water in a school, Zhejiang province

目的调查浙江省某学校出现多名急性胃肠炎病例的感染来源、传播途径和危险因素。方法可疑病例定义：2010年4月19—30日，该校学生和教职员工中出现腹泻（〉／3次／天）或呕吐者。确诊病例为可疑病例中用RT-PCR方法检出诺如病毒阳性者。开展病例对照研究，以流行高峰期21--23日的220例病例作为病例组，按年级1：1比例频数匹配，随机抽取同年级无症状的学生作为对照组，比较两组饮用桶装水类型、饮水习惯和饮用量、卫生习惯的差异。结果该校学生罹患率为20．3％（312／1536），教职员工无病例。98．6％的病例（n=217）和85．5％的对照（n=188）曾饮用过教室桶装水（OR。=12．3，95％C1：3．7～40．9）；其中47．9％的病例（n：104）和41．5％的对照（n=78）饮用过教室桶装水的冷水（ORM-H=3．8，95％CI：1．5～9．6）；47．9％的病例（n=104）和48．4％的对照（n=91）饮用过教室桶装水的冷热混合水（ORM-H=2．8，95％CI：1．1．7．0）。未开封的教室桶装水菌落总数和大肠菌群严重超标。3例病例的粪便及1份未开封的教室桶装水标本检出诺如病毒Ⅱ型核酸阳性。桶装水生产厂家属无证非法生产。结论本次暴发疫情由诺如病毒污染的教室桶装山泉水引起。建议学校停用桶装水、提供开水及非法生产厂家停止生产。

Objective To study a local hospital reported acute gastroenteritis in a boarding school on its source of infection, mode of transmission and risk factors of the infection. Methods A suspected case was defined as who had developed diarrhea （ ≥3 times/day） or vomiting among teachers or students of the school, during April 19-30,2010. A confirmed case was from a probable case plus tested positive for norovirus in stool specimens by using RT-PCR. Stool specimens of cases and environmental specimens were collected for laboratory diagnosis. In a case-control study, we compared exposures to sources of bottled water, consumption of bottled water, and hygienic habits of 220 probable or confirmed cases from April 21-23 in the peak of the outbreak, together with another 220 controls, with frequency-matched by school grade. Results 20.3% of the 1536 students but none of the teachers developed the disease. 98.6% of the cases （n=217） and 85.5% （n=188） of the controls had drunk bottled water in the classroom （ORM-H= 12.3,95%CI： 3.7-40.9）. 47.9% （n= 104） of the cases and 41.5% （n=78）of the controls had drunk unboiled bottled water in classroom （ORM..=3.8,95%CI： 1.5-9.6）. 47.9% （n=104） of the cases and 48.4% （n=91） of the controls had drtmk bottled mixed water （boiled and unboiled） in the classroom （ORM-H=2.8, 95% CI： 1.1-7.0）. Stool specimens from 3 cases and one bottle of uncovered bottled water in classroom showed positive of having norovirus genotype Ⅱ. Coliforms was cultured much higher rates than standard deviations in the bottled water. The factory making the bottled water was not licensed or having strict disinfection facilities. Conclusion Bottled spring water contaminated by norovirus was responsible for this outbreak.