一起急性呼吸道感染症暴发疫情的病原学和流行病学研究

Study on pathogen and epidemiology for the outbreak of an acute respiratory infectious disease

目的:对一起急性呼吸道感染症暴发疫情进行流行病学和病原学研究,以明确诊断,控制疫情。方法:通过流行病学调查描述疫情流行特征;采用病例对照研究分析流行因素;患者的咽拭子标本中提取核酸;PCR法检测病毒特异性基因片段;组织培养法(Hep-2细胞)分离病毒;电子显微镜观察病毒形态;型特异血清及型特异引物鉴定分离毒株型别;中和实验检测患者急性期和恢复期血清抗体效价。结果:疫情报告病例871例,波及10个乡镇,主要为在校中小学及幼儿园学生(占94.37%),具有班级聚集性。病例对照研究显示危险因素为与病人的接触、与鸡接触及家庭内共用毛巾等。35份咽拭子标本分离出15株病毒,分离阳性率42.9%。分离病毒经鉴定为腺病毒3型。PCR法检测腺病毒DNA,112份咽拭子标本中68份阳性,阳性率60.7%。18例双份血清中13例中和效价呈4倍以上增长或转阳,阳性率72.2%。对病毒进行全基因序列测定,确定为腺病毒3型。结论:本起急性呼吸道感染症暴发疫情由腺病毒3型引起,传播途径以呼吸道传播和密切接触为主。

Objective.. A study on pathogen and epidemiology for the outbreak of an acute respiratory infectious disease was done, so as to diagnose correctly in time and to control epidemic situation effectively. Methods： To describe the epidemic characteristics by the way of epidemiological investigation. The epidemic factors were analyzed by the method of Case-Control study. The nucleic acid was extracted from the throat swabs of patients and the gene segments were examined by PCR. The throat swabs of patients were inoculated into the Hep-2 cell cultures to isolate unknown virus. The viral cultures were observed by Electron Microscope. Serotype specific serum and type specific primes of human adenovirus were used to identify the isolated strains. The value of antibody in paired acute and convalescent sera from the sufferers was tested by neutralization assay. Results：The contagious dis- ease was spread to 10 township or villages and the cases were 871 totally. The most sufferers were students in the elementary schools and the kindergartens. The cases were clustered in classes. Being exposed to the fever cases as well as chickens, using the same towel within family members, which listed as the risk factors. The above mentioned results were acquired by the way of case-control study. 15 strains of human adenovirus type 3 were isolated from 35 throat swab samples and the isolation rate of the virus was 42. 9%（15/35）. The specific DNA fragments of human adenovirus were detected by PCR and the positive rate is 60. 7 % （68/112）. 72.2 % （13/18） of serum pair of patients show seroconversion or a four-fold rise in the neutralization antibody titer against the antigens. The whole virus gene was measured and adenovirus type 3 was confirmed. Conclusion： Human Adenovirus type 3 resulted the outbreak of the upper respiratory tract infection. The tracks of spread were mostly through aspiratory tract and consanguineous contact.