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目的通过连续的监测,了解北京地区婴幼儿甲型流感的流行规律。方法2001年- 10月-2005年8月,采集门诊和住院急性呼吸道感染患儿的标本7338份,分别经传代狗肾细胞进行病毒分离和(或)间接免疫荧光、血凝抑制试验进行流感病毒型别鉴定,采用RT—PCR方法,扩增甲3型流感病毒流行株的血凝素基因HA1区,进行序列分析。结果(1)从7338份临床标本中,检出甲型流感病毒347份,总阳性率为4．7％。347份甲型流感病毒中,甲1型48份(13．8％);甲3型273份(78．7％);暂时无法鉴定亚型的26份(7．5％)。(2)2001-2004年的流行比较局限在当年10月至次年4月,2004年8月-2005年8月均有甲型流感病毒被检测到,在夏季仍可检测到相当多的甲型病毒,尤其是2005年8月甲3型的阳性率达到14．2％,相当于2003-2004年的流行最高峰。4年中每个流行季节都以甲3型流感病毒的流行为主,只在2001-2002年和2004-2005年的流行季节出现了甲1型流感病毒的流行峰。(3)甲1和甲3型流感病毒在门诊患儿中的阳性检出率均高于住院患儿的阳性检出率。在2003年11月-2005年8月期间的236例甲3型感染患儿中,≤2岁者占46．6％,>5岁者占14．0％;而31例甲1型感染患儿中≤2岁者只占6．5％,>5岁者占48．0％。(4)对1998-2005年的甲3型流感病毒血凝素基因HA1区的序列分析显示,每一年的甲3型病毒都会出现位于其抗原决定簇关键位点的氨基酸突变。结论2001年10月-2005年8月,北京地区婴幼儿中有甲1和甲3型流感不同程度的流行,甲3型为优势流行株;2004-2005年北京地区甲型流感呈全年的流行态势;氨基酸序列分析提示,1998-2005年期间甲3型流感病毒的抗原性在持续不断地发生漂移。
Objective To understand the prevalence of influenza A and B in infants and young children in Beijing through continuous monitoring. Methods From July 2001 to October 2005, 7338 samples of outpatients and inpatients with acute respiratory infection were collected and divided into three groups according to virus isolation and / or indirect immunofluorescence and hemagglutination inhibition test Type identification. The hemagglutinin gene HA1 region of influenza A virus type 3 influenza virus was amplified by RT-PCR and sequenced. Results (1) From 7338 clinical samples, 347 influenza A viruses were detected with a total positive rate of 4.7%. Of the 347 influenza A viruses, 48 (13.8%) were type A and 273 (78.7%) were type A; 26 (7.5%) were not identified for the time being. (2) Comparison of prevalence in 2001-2004 The influenza A virus was detected from October to April in the same year, from August 2004 to August 2005, and quite a few cases were still detected in summer The positive rate of type A virus, especially type A virus in August 2005, reached 14.2%, equivalent to the highest prevalence in 2003-2004. Influenza A (Influenza virus type A) prevalence was observed in each of the four seasons in each of the four years. The epidemic peak of influenza A virus type 1 occurred only in the epidemic season of 2001-2002 and 2004-2005. (3) The positive detection rates of H1N1 and influenza A virus type 3 in outpatients were higher than those in hospitalized children. Of the 236 patients with type 3 infection between November 2003 and August 2005, 46.6% were younger than 2 years and 14.0% were older than 5 years. In 31 patients with type A infection Children ≤ 2 years old accounted for only 6.5%,> 5 years accounted for 48.0%. (4) Sequence analysis of HA1 region of influenza A virus type 3 hemagglutinin gene from 1998 to 2005 showed that each year of type A virus will have amino acid mutation located at the key site of its antigenic determinant. Conclusion From October 2001 to August 2005, there were different prevalences of Influenza A (H1N1) and Influenza A (H1N1) in infants and young children in Beijing. Influenza A (A) was the predominant endemic strain. Influenza A (H1N1) in Beijing during 2004-2005 showed an annual Epidemic situation; Amino acid sequence analysis suggested that during 1998-2005, the antigenicity of Influenza A (3) virus continued to drift.