北京市首例人感染H9N2禽流感病例的流行病学调查

Epidemiological investigation of the first case of human avian influenza A （H9N2） virus infection in Beijing

目的分析2016年12月北京市朝阳区确诊的1例人感染H9N2禽流感病例流行病学特征。方法访谈病例发病前后的相关知情人，调查病例发病经过和可能感染来源。采集病例、密切接触者及环境标本，应用实时荧光定量PCR（real—timePCR）方法，检测甲型流感病毒及H9N2禽流感病毒特异的核酸片段。对病例咽拭子标本和1件阳性环境标本中的H9N2禽流感病毒血凝素（Hemagglutinin，HA）基因进行序列测定和分析。结果病例表现为轻症流感样病例症状，发病前15天曾有活禽市场暴露史。该市场环境标本中H9N2禽流感病毒阳性率为18．2％（2／11）。病例咽拭子标本与市场环境标本中病毒的HA基因高度同源，氨基酸相似度为100％，在进化关系上同属于欧亚系的Y280分支。4名密切接触者在医学观察期内未出现过发热、咳嗽等呼吸道症状。结论病例感染来源与活禽市场环境暴露有关。加强流感监测以及活禽市场的管理对于防控人感染禽流感疫情具有重要意义。

Objective To investigate （H9N2） virus infection in Beijing. Methods and to analyze the first human case of avian influenza A The relatives of the case were interviewed to investigate the process of morbidity and possible infection sources. Samples of the case, close contacts as well as environmental samples were collected and were tested by real-time PCR for nucleic acids of influenza A （H9N2） virus. Hemagglutinin （HA） genes of the viruses from the case and environment samples were sequenced and analyzed. Results The main clinical manifestations of the case were wild influenzalike symptoms and signs, with a history of exposure to live poultry market 15 days prior to the onset of illness. The positive rate of avian influenza A （H9N2） virus collected from that market was 18.2%.Based on the phylogenetic analyses, the amino acid homology between the viruses isolated from the case and environment reached 100%, and both of them belonged to the Eurasian lineage. Neither fever nor respiratory symptoms were found in all 4 close contacts during the medical observation period. Conclusions This case of avian influenza A （H9N2） virus infection was associated with exposure to live poultry market. Enhanced surveillance for influenza and supervision for live poultry market is important to the prevention and control of avian influenza infections.