Epidemiology and pathogen study of an outbreak in clusters caused by human adenovirus type 4 in Shenzhen

Objective To analyze the epidemiological and pathogenetic characteristics of a community outbreak of acute respiratory tract infection by Human adenovirus serotype 4 (HAdV-4) at a primary school in Baoan district, Shenzhen, Feb.22-28, 2019. Methods All epidemiological and clinical information of these cases was collected through field interviews and medical records. Throat swabs samples were collected and tested for influenza virus in quantitative fluorescence PCR. Influenza virus negative samples were then PCR tested for 6 other common respiratory virus. HAdV-4 positive samples were further tested using hexon gene sequencing of adenovirus. The sequences were aligned with the GenBank data to determine the genotypes and draw the phylogenetic tree. Results The epidemic occurred in Class 1, Grade 2, with a total of 54 students, including 29 boys and 25 girls. After investigation, there were no cases of similar symptoms in other classes of the school. Totally 13 patients were diagnosed, including 7 boys and 6 girls, the incidence rate was 24.1%(7 / 29) and 24.0% (6/25), respectively. The clinical symptoms included fever (13 cases, 100.0%), sore throat (8, 61.5%), muscular ache (8, 61.5%) and cough (5, 38.5%). All the symptoms were mild, and there were no severe cases. All 5 throat swabs samples were adenovirus positive by PCR, and these positive samples were confirmed to be HAdV-4 subgroups E by DNA sequence analysis. Conclusion The acute respiratory infection outbreak was caused by HAdV-4. The sequence of the strain is highly homologous with sequences from other districts of Shenzhen and Chinese cities. 摘要：目的 分析2019年2月22—28日深圳市宝安区某小学一起急性呼吸道病毒感染聚集性疫情的流行病学及 病原学特点。 方法 采用流行病学个案调査表对疫情进行现场调査, 使用荧光定量 PCR 方法对采集的咽拭子标本进 行流感样病例病原学筛査, 筛査阴性标本进行6种常见呼吸道病毒核酸检测。对腺病毒核酸阳性的标本, 用腺病毒六 邻体基因作为靶基因进行序列扩增及测定, 测序结果在GenBank上进行序列比较, 确定其病毒亚型并进行系统进化分 析。 结果 疫情发生在二年级(1)班, 全班共54名学生, 男29名, 女25名。经调査该学校其他班级其余年级未出现相 同症状病例。该起疫情共发现病例13例, 其中男生7例, 女生6例, 男女学生罹患率分别为24.1%( 7 /29)和24.0% ( 6 /25)。临床特征为发热13例(100.0%), 咽痛8例(61.5%), 全身肌肉酸痛8例(61.5%), 咳嗽5例(38.5%), 症状均较轻, 无重 症病例。共采集5份咽拭子标本 , 经荧光定量PCR检测均为腺病毒核酸阳性 , 5份标本用分型引物检测并分析序列确 定均为腺病毒E亚属4型。 结论 此次急性呼吸道感染聚集性疫情由腺病毒4型引起, 毒株序列与深圳其他区、国内 其他城市分离的腺病毒4型毒株序列具有髙度同源性。