北京市2009年甲型H1N1流感患者密切接触者的流行病学特点

Epidemiological characteristics of infection for close contacts of pandemic （ H1N1 ） 2009 in Beijing

目的了解和掌握甲型HlNl流感患者密切接触者的流行病学特点，为未来流感大流行的防控提供可参考的依据。方法选择2009年5月16日至9月15日北京发现的613例具有明确密切接触者信息的甲型H1N1流感患者（原发病例）及其密切接触者7099名作为研究对象，根据其流行病学调查资料和标本资料收集相关信息，对甲型H1N1流感密切接触者的感染情况进行描述性分析。通过X^2检验对不同类型甲型H1N1流感密切接触者的感染情况进行比较分析。结果613例原发病例中，男348例（56．8％），女265例（43．2％），年龄为1～75岁，中位年龄为20岁。7099名密切接触者中，男3518名（49．6％），女3514名（49．5％），性别不详67名（0．9％），年龄为0-99岁，中位年龄为27岁。甲型HlN1流感原发病例密切接触者的感染率为2．4％（167／7099）。随着密切接触者年龄的增长，甲型H1N1流感病毒感染率呈现明显下降的趋势（X^2=27．87，P〈0．001）；以不同方式与原发病例接触的密切接触者之间的感染率比较差异有统计学意义（X^2=109．76，P〈0．001）。甲型H1Nl流感原发病例的密切接触者中，隐性感染病例占14．4％（24／167）。对于密切接触者中出现症状的感染者，最早可在发病前4．5d的咽拭子标本中检测到病毒；病毒传代时间的中位天数为2．4d。结论甲型H1N1流感原发病例密切接触者的病毒感染率较低；不同年龄及不同接触方式的密切接触者之间的感染率存在差异；14．4％的甲型H1N1流感病毒感染者为隐性感染；甲型H1N1流感病例有可能在发病前4．5d即具有传染性。

Objective To examine the epidemiological characteristics of infection for close contacts of pandemic （H1N1） 2009 and to provide scientific evidence for preparedness and response for the next pandemic. Methods A total of 613 index cases with clear information of close contacts and their 7099 close contacts, determined between May 16 and September 15, 2009, were included in this study. Based on data of epidemiological investigation, sampling and test of index cases and close contacts, the characteristics of infection for close contacts were described. Results 56. 8% （348/613） of the index cases were male, and 43.2% （265/613） were female, and the median age was 20 years （range： 1-75 years ）. 49. 6% （3518/ 7099） of the close contacts were male, and 49. 5% （3514/7099） were female, but the sex information of 0. 9% （67/7099） could not be recorded. The median age of the close contacts was 27 years （range： 0-99 years ）. 2.4% （167/7099） of close contacts were infected. The attack rates decreased with increasing age of close contacts（ X^2 = 27.87, P 〈 0. 001 ） , and were significantly different between various contact patterns of close contacts（ X^2 = 109. 76, P 〈0. 001 ）. 14.4% of the infected close contacts were asymptomatic. For close contacts with symptomatic infection, virus could be shed 4. 5 days before illness onset, and the mediangeneration time was 2. 4 days. Conclusion The attack rate of close contacts was very low; and the attack rates were different between various ages and contact patterns of close contacts. In this series 14% of cases with pandemic（ H1N1 ） 2009 were asymptomatic. The symptomatic cases might have infectivity 1 day earlier before illness onset.