一起细菌性痢疾暴发疫情的流行病学调查

Epidemiological investigation of an outbreak of shigella sonnei

目的核实疫情,调查疫情发生的原因,找出可能的危险因素,提出防制建议,控制疫情蔓延。方法开展现况调查,调查发病和学生饮食饮水情况,收集实验室检测结果;开展病例对照调查,在符合条件的病例中选取30份为调查对象,按1∶1比例随机选取与被选取病例同校同班的无症状学生,找出可能的危险因素。结果2007年12月19日至2008年1月5日共发生病例120例,总罹患率为8.6%,学生发病117例,罹患率为8.9%,初中和小学学生罹患率分别为10.2%,7.9%,差异无统计学意义(χ2=2.08,P>0.05);另有3名教职工发病,罹患率为3.5%。22例从粪便中检测出福氏志贺菌(4a型);喝生水为危险因素(OR=3.0,95%CI:1.1～7.6),使用2号井水OR=3.2,95%CI:1.2～8.6,使用3号井水OR=2.0,95%CI:1.0～3.7。结论本次疫情为一起福氏志贺菌(4a型)感染所致的水源性菌痢暴发流行,使用2号和3号井水是本次疫情暴发的因素。

Objective To verify an outbreak of dysentery in two schools, identify the possible source of infection, the mode of transmission and recommend measures for the disease control. Methods We investigated the history of water consumption of cases and controls after December 10, focusing on the water supplying sources for the schools. A case-control study was used to investigate risk factors and a cohort study was used to validate risk factors. Results 37% of students in case group and 17% of students in control group had drunk non-boiled well water as reported （ OR = 3.0, 95% CI： 1.1 - 7. 6 ） . 10% （ 107/1 052） of the students had the disease with consumption of water from well 3 while 5.2% （ 10/193 ） of the students had the disease without consumption of water from the well. （RR = 1.9, 95% CI： 1.0 -3.7） ; 12. 5% （55/440） of the students had the disease with consumption of water from well 2 while 3.9% （4/102） of the students had the disease without consumption of water from the well （RR =3.2, 95% CI： 1.2 -8. 6） . 22 of 120 stool samples from the cases were confirmed to be positive for Shigella sonnei （4a） by culture. Fecal coliforms were greater than 1600/100 ml for water collected from well 3 on December 24, 2008. Conclusion The outbreak of Shigella dysentery was caused by polluted well water. The local government reconstructed the water supply system for the schools in response to the report.