一起诺如病毒感染引起的职业学校暴发疫情分析

Analysis of an outbreak of norovirus infection in a vocational school

目的 分析南京市一起职业学校诺如病毒感染暴发疫情特征,探讨调查处置经验。方法 通过现场流行病学方法搜集信息,应用描述性流行病学方法分析疫情流行病学特征,采集疑似病例及无症状人员肛拭子、环境、食物标本,进行病原学检测。结果 搜索到疑似病例96例,其中确定临床诊断病例90例,确诊病例6例,全校患病率为9.50%(96/1 010)。男生患病率为18.60%,高于女生的9.05%(χ~2=7.947,P<0.01)。寄宿生患病率为11.10%,高于走读生的4.79%(χ~2=6.061,P<0.05)。疑似病例诺如病毒核酸检测阳性率22.22%(6/27),无症状人员阳性率12.20%(5/41),二者差异无统计学意义(χ~2=1.207,P=0.324)。4名食堂无症状感染员工于首次检测诺如病毒GⅡ型阳性1周后(4月15日)再次采集肛拭子进行核酸检测,仍有2人为GⅡ型诺如病毒阳性,副溶血性弧菌、沙门氏菌、金黄色葡萄球菌和志贺氏菌4种致病均未检出。结论 该起事件可能是由GⅡ型诺如病毒引起的校园急性胃肠炎暴发疫情,应加强无症状感染者携带诺如病毒的监测。

Objective To analyze the characteristics of an outbreak of norovirus infection in a vocational school in Nanjing City and explore the experience of investigation and disposal.Methods Information was collected by field epidemiological methods,descriptive epidemiological methods were used to analyze the epidemiological characteristics of the epidemic,and swabs,environmental,and food samples of suspected cases and asymptomatic people were collected for pathogenic detection.Results A total of 96 suspected cases were found,including 90 clinically diagnosed cases and 6 confirmed cases.The prevalence rate in the school was 9.50%(96/1 010).The prevalence in boys was 18.60%,higher than that of girls:9.05%(χ~2= 7.947,P < 0.01).The prevalence of boarders was 11.10%,higher than that of day students:4.79%(χ~2= 6.061,P < 0.05).The positive rate of norovirus nucleic acid test in suspected cases was 22.22%(6/27) and the positive rate of asymptomatic people was 12.20%(5/41),and the difference between the two was not statistically significant(χ~2= 1.207,P =0.324).One week after the first positive test for type GⅡ norovirus(April 15),the anal swabs were collected from 4 asymptomatic infected cafeteria employees again for the nucleic acid test,and 2 of them were still positive for type GⅡ norovirus.Vibrio parahaemolyticus,Salmonella,Staphylococcus aureus,and Shigella were not detected.Conclusions This incident may be an outbreak of acute gastroenteritis on campus caused by norovirus type GⅡ.Surveillance for norovirus in asymptomatic carriers should be strengthened.