宝安区一起学校水痘爆发的流行病学调查

Investigation and Analysis of An Outbreak of Chickenpox in A School of Bao′an District

目的调查分析一起水痘爆发疫情的原因和特点,总结经验教训。方法病例定义为2007年2月28日以来,学校内教师和学生中出现典型的水痘样皮疹(疱疹≥3d),伴或无发热症状体征。通过现场调查、问表等方法,描述本次爆发的流行病学特征,通过病例对照研究危险因素。结果123例患者中罹患率为6.8%,其中男6.7%,女7.0%。流行病曲线上发病最高点在4月30日到5月3日。三年级的罹患率为20.1%,一年级的罹患率为16.2%。患病的主要危险因素为:中午两小时午休时间(RR=4.9,95%CI=3.4-7.1)和乘坐校巴时(RR=3.2,95%CI=2.3-4.5)的密切接触。对27个班级的940名学生进行进一步分析发现,只在学校午休而不乘校巴的(RR=5.4,95%CI=3.5-8.3);在校午休同时也乘校巴(RR=2.8,95%CI=1.9-4.2)。对午休的57个宿舍进行人群聚集性分析有显著性意义。结论此次水痘爆发的主要危险因素与学生中午两小时午休期间在宿舍聚集和乘坐校巴时的密切接触有关。有效的控制措施是对病例的隔离及学校和校巴的消毒。

Objective This investigation was to analyze the risk factors and epidemiological characteristics of one outbreak of chickenpox. Method The case was defined as getting chickenpox-like herpes within more than three days with or without slight fever among the teachers and students in Longhua foreign language-experimental school on Feb.28. By means of field epidemiology investigation and case-control study, the epidemiology characteristics and the risk factors were explored. Result 123 cases were found in 1797 kids in 42 classes from grade 1 to 12, and identified as chickenpox （clinical or laboratory diagnosis）, whose attack dates were from Feb.28 to May.21. The attack rate is 6.8% （male 6.7%, female 7.0%）. The highest peak of outbreak occurred during Apt 30 to May 3. The attack rate is 20.1% in grade 3, and 16.2% in grade 1. Both taking 2-hour break at noon in dormitories （RR=4.9, 95%CI=3.4- 7.1） and taking the school bus （RR=3.2, 95%CI=2.3-4.5） are significant risk factors. The stratified analysis on the status of taking break at noon and taking the school bus among 1501 kids from 42 classes shows the RR value of taking break at noon without taking school bus （RR=7.9, 95%CI=5.1-12.4 ） is higher than that of taking break at noon and by bus （RR=4.03, 95%CI=2.7-6.6）. The further stratified analysis among 940 kids from 27 classes with cases shows taking break at noon without taking bus （RR=5.4, 95%CI=3.5-8.3） is more important than taking break at noon and taking bus （RR=2.8, 95%CI=1.9-4.2）. The cluster analysis for cases who take 2-hour break at noon in 57 dormitories shows there was obvious clustering among these cases （P〈0.O1）. Four indexes and their modes of transmission were found during sporadic period. Conclusion There is an outbreak of chickenpox in a school from Apr. 26 to May 15; the risk factors include contacts in dormitories for 2-hour break at noon and taking school bus. The effective measures arc disinfection of classrooms, school buses and dormitories and isolation of the infected cases till recovery.