某学校诺如病毒暴发调查

Survey on norovirus outbreaks in a school

目的调查沈阳市某学校连续2起诺如病毒暴发疫情,了解暴发原因及危险因素。寻找防控措施中可能存在的疏漏,为诺如病毒暴发疫情的处置提供经验,为有效控制疫情提供科学依据。方法按照病例定义标准开展病例搜索,对病例进行流行病学调查;对采集的样本进行荧光定量聚合酶链式反应(PCR)核酸检测。结果第1起疫情波及173人,其中学生171人,教师2人,罹患率为10.67%(173/1 621);第2起疫情波及71人,均为学生,罹患率为4.90%(71/1 448)。2起疫情的临床症状均以恶心、腹痛、腹泻、呕吐为主,第1起疫情发热、呕吐症状与第2起疫情比较差异有统计学意义(P <0.01)。第1起疫情首发病例出现在4月17日,发病高峰期为4月21日,占60.69%(105/173);第2起疫情的首发病例出现在4月30日,发病高峰期为5月3日,占57.75%(41/71)。第1起疫情发病前5位的班级病例数共59例(占34.10%),教学楼B座2层、4层发病人数分别占32.95%、33.53%;第2起疫情发病前4位的班级病例数共37例(占52.11%),教学楼B座2层发病人数占73.24%。2起疫情均为2号公寓(2年级)4层发病人数最多(30例、占17.34%,20例、占28.17%)。学生病例和后厨工作人员肛拭样本诺如病毒阳性率分别为29.55%和30.43%。结论 2起诺如病毒疫情病例具有明显的班级、教学楼楼层和公寓楼层聚集性,存在食堂工作人员感染情况。

Objective To investigate two consecutive norovirus outbreaks in a school in Shenyang city,understand the causes and risk factors,and find out the possible omission in prevention and control measures,so as to provide scientific basis for the effect disposal of norovirus outbreak. Methods Case-finding was carried out according to the standard of case definition,and epidemiological investigation was conducted;samples were collected and tested by fluorescence quantitative polymerase chain reaction(PCR)nucleic acid detection. Results A total of 173 cases were found in the first outbreak,including 171 students and 2 teachers,with attack rate of 10.67%;there were 71 students in the second outbreak,with the attack rate of 4.90%.The main clinical symptoms of the two outbreaks were nausea,abdominal pain,diarrhea and vomiting.There were significant differences in fever and vomiting between the first and the second outbreak(P <0.01).The first case in the first outbreak occurred in April 17th,and the cases concentrated in April 21th,accounting for 60.69%(105/173);in the second outbreak,the first case occurred in April 30th,and epidemic peaked in May 3rd,accounting for 57.75%(41/71).There were 59 patients(34.10%) in the top five classes of case number in the first outbreak,cases on the second floor and the fourth floor of block B of the teaching building accounted for 32.95% and 33.53%,respectively.In the second outbreak,there were 37 cases (52.11%)in the top four classes of case number,cases on the second floor of block B of the teaching building accounted for 73.24%.Both of the outbreaks had the largest number of cases on the fourth floor of apartment 2,with the constituent ratios of 17.34%(30 cases) and 28.17%(20 cases)respectively.The norovirus positive rate in the samples of anal swabs collected from the cases and the kitchen staff were 29.55% and 30.43%respectively. Conclusion The two norovirus outbreaks show obvious aggregation in classes,floors of teaching buildings and apartments.There is infection in the canteen staff.