一例H5N1人禽流感病例感染源调查分析

Investigation on the source of infection regarding an avian influenza （H5N1） case in Hong Kong that returning from Guangzhou

目的明确1例人禽流感H5N1确诊病例的感染来源。方法通过现场流行病学调查、密切接触者医学观察、高危从业人员症状监测、实验室检测和溯源调查等方法，判断感染来源。结果2012年5月17—19日该患儿随母在广州A市场购买活鸭，现场经历屠宰过程。23、24日发病后在当地医院就诊，诊断为呼吸道感染；26日抵香港后诊断为人禽流感病例。23名密切接触者和34名市场禽类销售屠宰从业人员未出现流感样症状。患儿住家附近B市场2名禽类销售人员H9型血清抗体阳性，阳性率为6．06％（2／33）。A、B两市场砧板、禽笼等环境标本H5、H9型阳性率分别为9．8％（5／51）和2．0％（1／51）。B市场一份砧板H5型阳性标本与患儿标本同属2．3．2．1分支。B市场阳性档口的进货来源与A市场一致。结论该禽流感病例的感染来源为广州市肉菜市场禽类销售档口。

Objective We conducted an epidemiologic investigation to determine the source of infection on an avian influenza （H5N1） case who returned from Guangzhou, in Hong Kong. Methods Data related to epidemiologic investigation, medical observation on close contacts, Syndromic Surveillance on poultry salesmen, emergency monitoring, detection of the samples, source tracing on potential Avian influenza virus （H5, H7, H9） infected people, situation on environment pollution by avian influenza virus in the markets etc. were gathered. The determination of infection source was through comparing the different genes between the case and positive environmental samples. Results The infected case witnessed the procedure of how a live duck was killed, in market A in Guangzhou during May 17th to 19th. The case was diagnosed as respiratory tract infection in 2 Third-grade-Class A hospitals in Guangzhou on May 23th and 24th. The diagnosis was made as Avian influenza cases on May 26th after going back to Hong Kong. 23 close contacts and 34 markets poultry salesmen did not show any ILI related symptoms. However, 2 poultry salesmen from the markets nearby the place where the Avian influenza case stayed, were detected having positive H9 avian influenza antibody, with the H9 positive rate as 6.06% （2/33）. Among the environmental samples in the 2 markets nearby home of the patient, chopping block was found to have carried H5, with positive rate as 9.8% （5/51 ） while poultry cage was found to carry H9, with the positive rate as 2.0% （1/51 ）. A H5 positive sample was found with clade 2.3.2.1, same to the case, from a chopping block at the market B where the sources of poultry was the same as market A. Conclusion The source of infection seemed to come from the markets in Guangzhou, that calling for the strengthening of poultry market management, for avian influenza prevention. History related to contact of poultry should be gathered when a diagnosis of respiratory tract infection was made. Timely sampling and testing should be made to improve the sensitivity of diagnosis.