一起学校甲型副伤寒暴发疫情流行因素分析

目的　查明一起学校甲型副伤寒暴发疫情的流行因素。方法　通过查询有关医疗机构的门诊和住院登记记录、每日报告新发病例等方法搜索病例，描述疫情的流行强度和三间分布；用分析流行病学，分别对高中生与初中生、住校生与通校生、男性与女性等不同人群的发病情况进行比较；同时开展现场卫生学调查，寻找病因线索；选择实验室确诊的学生病例44例为病例组，与病例同性别、同班级、同走读或住校、9月份以来没有发热的学生88人为对照组，开展1∶2配对的病例对照研究，查找疾病流行的危险因素。结果　从2007年9月20日至10月23日，该校共报告甲型副伤寒病例122例，罹患率为8.2％，4例并发中毒性肝炎或肾炎，其他患者病情均较轻，经住院隔离治疗后全部病例治愈出院，无死亡；高中生罹患率（10.6%）高于初中生（6.7%），2周内在学校周围饮食店就餐史（OR:6.60，X2＝10.29，P=0.001）和2周内与同学有拼餐史（OR:4.93，X2＝5.11，P=0.020）为本次暴发的危险因素。结论　2周内外出学校周围饮食店就餐是引起此次疫情的主要危险因素；学生拼餐和生活密切接触分别是疫情前期和后期造成人相互传播，促进疫情的扩散的危险因素。

Epidemiological analysis of an outbreak of paratyphoid A in a school

Objective The study was conducted to investigate the epidemiological factors related to the outbreak of paratyphoid A in a school in order to provide evidence for the development of corresponding preventive and control strategies.Methods The epidemic strength as well as temporal,regional and population distribution was described based on clinical and in-hospital registration records and newly reported cases each day.Epidemiological analysis was performed to compare the incidences in senior versus junior school students,school-living students versus commuters and male versus female.Field health survey was also carried out to identify the cause of disease.A total of 44 affected students whose diagnosis was laboratory-confirmed were enrolled in the case group in 1:2 matches to the control group that included 88 students of the same sex,class and living arrangement who had no history of fever since September.Results A total of 122 patients were reported form Sep.20 to Oct.23 in 2007,the attack rate being 8.2%.Four patients were complicated with toxic hepatitis or nephritis,and other ones were milder.After isolation and treatment,all cases recovered and were discharged with no death cases.The attack rate of senior high school students was 10.6%,higher than that of junior high school students(6.7%).Having meal in restaurants around the school(OR:6.60,X2=10.29,P=0.001) and having meal with other classmates(OR:4.93,X2=5.11,P=0.020)of the past two weeks were the risk factors associated with this outbreak.Conclusion Having meal in restaurants around the school in the past two weeks was the primary risk factor of this outbreak.Having meal with other classmates and close contact were the risk factors associated with prophase and anaphase human-to-human transmission and spread,respectively.