北京地区2009-2010年乙型流感病毒的流行特征及HA1基因片段特性分析

Distribution of Influenza B virus and characterization of HA1 segment in Beijing during 2009-2010

目的了解2009年5月-2010年4月间北京地区乙型流感的流行特征及血凝素（HA1）变异情况。方法采用real-time RT-PCR法对流感样疑似病人咽拭子进行乙型流感病毒检测,采用DNA Star软件对HA1基因片段核苷酸和氨基酸序列进行系统进化分析。结果 2009年5月-2010年4月共收集并检测流感样疑似病例咽拭子样本2 138份,乙型流感病毒阳性169例,总阳性率为7.9%,且以2010年2月阳性率最高。乙型流感病毒阳性者平均年龄为（35±24）岁,显著高于对照组中的（28±19）岁（P〈0.001）;女性组中乙型流感病毒阳性率为11.8%,显著高于男性组的7.9%（P〈0.015）。HA1片段序列分析显示本地区的乙型流感病毒属于Victoria系,与参考株B/Brisbane/60/2008相比,其核苷酸、氨基酸的同源性分别为93.4%-99.2%和99.3%-99.7%;2个氨基酸发生改变。结论 2009年5月-2010年4月期间北京地区乙型流感病毒的流行高峰为2010年1、2月,主要累及的人群为35岁以上的女性。本地区的优势流行株仍属于Victoria系,其抗原性未发生明显改变,提示以往流感疫苗仍有较好的保护效果。

Objective To describe the population distribution of influenza B virus and analyze the genetic characteristics of hemagglutin（HA） gene.Methods Nasopharyngeal swabs were collected from influenza like illness（ILI） patients in the General Hospital of PLA（Beijing） between May,2009 to April,2010.The assay of real-time RT-PCR and nested RT-PCR were used for influenza B virus sequencing.The method of phylogenetic analysis was used to align the nucleotide and amino acid sequences with DNA star software.Results A total of 2 138 nasopharyngeal swabs were tested and 169 were positive for influenza B virus.The highest positive proportion of type B virus was found on February,2010.The mean age of the cases（35±24）years were significantly higher than that（28±19）years of test negative group（P〈0.001）.The positive proportion of type B virus infection was significantly higher in female（11.8%） than that in male（7.9%,P〈0.015）.The phylogenetic analysis showed that the prevalent strains belonged to Victoria lineage and displayed identity of 93.4%~99.2% and 99.3%-99.7% at the level of nucleotide and amino acid sequences,respectively with the strain of B/Brisbane/60/2008.Two replaced amino acids were found in the determinant sites of HA gene.Conclusion The type B influenza virus had predominant distribution in female over 35 years old and peak appearance from January to February,2009.The prevalent strains of type B virus belonged to Victoria lineage,although the replacement of two amino acids was seen in the virus isolated from Beijing.