一起学校肺炎支原体感染聚集性疫情的调查分析

Investigation and analysis of a cluster outbreak of Mycoplasma pneumoniae infection in a school

  • 摘要:
    目的 调查和分析杭州市上城区某学校一起肺炎支原体(MP)感染聚集性疫情,为今后类似疫情防控提供参考。
    方法 制定病例定义并开展病例搜索,对搜索到的病例逐一进行电话随访。设计MP感染相关因素调查问卷,在疾病预防控制中心专业人员指导下自行填写问卷。采集病例和密切接触者咽拭子标本进行流感病毒、腺病毒、MP核酸检测。
    结果 该起疫情共发现病例28例,均为同一班级学生,该班级学生罹患率为68.29%,男生罹患率为66.67%(12/18),女性罹患率为69.57%(16/23)。临床表现以咳嗽(26例,92.86%)、发热(21例,75.00%)为主,中位发热天数为5 d,部分病例(20例,71.43%)有肺炎表现,有13例(46.43%)住院,中位住院时间为5 d,无重症和死亡病例。疫情共历时42 d,病例主要集中在11月6日—11月20日发病,共22例(78.57%)。感染相关因素调查显示,去校外人群密集的公共场所佩戴口罩为MP感染的保护因素(OR=0.27,95%CI:0.08~0.94,P=0.040),挑食为MP感染的危险因素(OR=8.60,95%CI:1.30~56.75,P=0.036)。综合病行病学史、临床症状和实验室检测结果,判断该起疫情为一起MP感染聚集性疫情,由首发病例院内感染后引起班内传播的可能性较大。
    结论 MP感染潜伏期长、传染性强、病情迁延、轻症和隐性感染比较高。建议疫情处置时降低疑似病例纳入标准,提高监测敏感性。根据潜伏期长短和疫情波及的范围制定停课标准,停课时长≥平均潜伏期(2周)。

     

    Abstract:
    Objective To investigate a cluster outbreak of Mycoplasma pneumoniae (MP) infection in a school in Shangcheng District, Hangzhou, and to provide references for the prevention and control of similar epidemics in the future.
    Methods Cases were defined and searched, and telephone follow-ups were conducted one by one for the searched cases. A questionnaire on the factors related to MP infection was designed to collect information, and the questionnaire was filled under the guidance of professionals from the centers for disease control and prevention (CDC). Throat swab samples from cases and their close contacts were collected for the detection of influenza virus, adenovirus and MP nucleic acids.
    Results A total of 28 cases were found in this outbreak, all of them were students from the same class, and the incidence rate of the students in the class was 68.29%, with an incidence rate of 66.67% (12/18) in male students and 69.57% (16/23) in female students. The main clinical manifestations were cough (26 cases, 92.86%) and fever (21 cases, 75.00%), with a median fever day of 5 days. A total of 20 cases (71.43%) had pneumonia, 13 cases (46.43%) were hospitalized, with a median hospitalization day of 5 days. There were no severe and fatal cases. The epidemic lasted for 42 days, and the cases were mainly concentrated between November 6 and November 20, with a total of 22 cases (78.57%). The investigation of infection factors showed that wearing a mask in public places with dense population out of school was a protective factor for MP infection (OR=0.27, 95%CI: 0.08‒0.94, P=0.040), and picky eating was a risk factor for MP infection (OR=8.60, 95%CI: 1.30‒56.75, P=0.036). Based on the comprehensive epidemiological history, clinical symptoms, and laboratory results of the cases, it is determined that the epidemic is a clustered outbreak of MP infection, with a high possibility of intra-class transmission caused by the first case of hospital infection.
    Conclusion The incubation period of MP infection is long, the infectivity is strong, the illness is prolonged, and the mild hidden infection rate are relatively high. It is suggested that the inclusion criteria for suspected cases should be lowered to improve the sensitivity of surveillance during the epidemic management. Class suspension criteria should be made based on the length of the incubation period and the extent of the outbreak, and which should be at least longer than the average incubation period (2 weeks).

     

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