集中式供水污染致诺如病毒感染性腹泻暴发的调查

目的 了解一起感染性腹泻暴发的病因、感染来源,采取针对性措施控制疫情蔓延.方法 对涉疫的Y镇北部5个村委会的现住居民进行回顾性队列研究,用统一的调查表登记2007年11月20日以来所有有腹泻或呕吐症状之一者.对Y镇北部5个村委会的供水系统、3个自然村的环境及部分患者家庭进行现场卫生学调查.面访部分病例.用Real-time PCR和巢式PCR方法 检测患者粪便标本诺如病毒核酸.结果 2007年11月24日至12月3日,Y镇北部饮用A自备自来水的村民共发生腹泻或呕吐病例435例,发病率12.93%.病例分布在饮用A自备自来水的所有村委会,最高发病率21.23%(100/471),最低5.21%(20J/3s4),饮用A自备自来水与发病之间有关联性(RR=9246,95%C/:6.25～13.68).发病时间集中在25-27日,占85.9%(262/305).调查S2村委会某自然村年龄别发病率分别为,0岁～组20.0%(3/15)、10岁～组17.3%(9/52)、20岁～15.2%(16/105)、60岁以上23.3%(7/30),各年龄组差异无统计学意义(X2=1.15,P>0.05).病例大多病情较轻,经门诊对症治疗后痊愈,无住院和死亡病例.现场调查和水质日常监测发现水处理过程存在消毒不落实的情况.A自备自来水水质检测细菌学指标不合格.患者2份呕吐物和1份粪便未检出沙门菌、志贺菌和金黄色葡萄球菌,3份患者粪便和3份患者肛拭诺如病毒检测,Real-timePCR 3份阳性,巢式PCR 6份阳性.对供水管网进行清洗消毒后病例迅速递减.采取消毒饮用水和健康教育等综合措施后,疫情迅速得到有效控制.结论 本次疫情为一起诺如病毒感染性腹泻暴发,可能是因A自备自来水受污染而引起的暴发.

Investigation of a norovirus outbreak through contaminated centralized water supply system

Objective To investigate the etiology and source of an infectious diarrhea outbreakand control the epidemic. Methods Through the retrospective cohort study, we had surveyed all the residents who complained symptoms of diarrhea or vomitting since Nov. 20th,2007 from the five villages in the north of town Y, and collected hygiene information on the water supply system of the five villages, the environment information of three villages and hygiene information of some case-indexed families, and tested the etiological biomarker, including nucleoside acid of norovirus through Real-time PCR and nested PCR technologies. Results From Nov. 24th to Dec. 3th in 2007, 435 diarrhea or vomitting cases were found in the north of Y town, where tap water A was supplied for daily use. The attack rate was 12.93%. The diarrhea eases were distributed among all country groups who has used tap water A and the attack rate was ranged from 5.21% (20/384) to 21.23% (100/471). Drinking the tap water A was significantly associated with an increased risk of infection(RR=9. 246,95% CI:6.25 -13.68). About 85.9% (262/ 305) of the cases were from Nov. 25th to 27th. An investigation of a country of S2 group showed that the incidence of different age groups was distributed as the following: 0 -year-old 20. 0% (3/15) ; 10 -year-old 17.3% (9/52) ; 20 -year-old 15.2% (16/105) ; older than 60 year-old 23.3% (7/30). No statistical significance was identified between age and infection(X2=1.15 ,P>0.05). Most of the patients were not serious and well prognostic, and no hospitalized or dead cases were reported. On site investigation and daily water quality monitoring showed that disinfection procedures were not strictly followed. The monitoring data also indicated the bacterio|ogy index of tap water A was disqualified. The test of Salmonella,ShigeUa and Staphylococcus aureus were negative in two vomit and one stool samples from patients. Three specimens by Real-time PCR, and six by nested PCR were positive for norovirus among the three feces and three anal swabs samples. With the drinking water sterilization and health education, the epidemic had been controlled rapidly and effectively. Conclusion The epidemic was a diarrhea outbreak that might be caused by norovirus through drinking the contaminated tap water A.