2.3.2.1c家系H5N1禽流感病毒在我国的持续传播与进化

Continuing spread and evolution of clade 2.3.2.1c H5N1 highly pathogenic avian influenza viruses in China

目的研究我国流行的H5N1高致病性禽流感病毒的进化与传播。方法从山东一养鸭场采集鸭粪标本,进行甲型流感PCR检测和分型,对阳性标本进行全基因组序列测定。对获取的全基因组序列进行系统发育分析,并研究其基因组的分子特征。结果 PCR检测有4份标本甲型流感病毒阳性,均为H5亚型,命名为A/Duck/Shandong/1-14/2014(H5N1)。病毒HA基因系统发育分析表明该病毒属于2.3.2.1c家系。测序分析表明,该病毒除了PB2基因来自H9N2亚型外,其余7个基因均来自H5N1。该毒株与北美首例人感染H5N1和造成2015年1月河南三门峡野鸟疫情的毒株属于同一个基因型。尚未发现该基因型毒株在关键氨基酸位点发生变异。结论 2014年山东分离株HA属于2.3.2.1c家系,为一新近报道的基因型。该基因型病毒于不同时间在我国的北京、山东和河南等地家禽和野鸟中出现,表明其已具备了一定的适应性并在持续传播。因此,应对该病毒的传播进行持续监测。

Objective This work was designed to study the continuing evolution and spread of the highly pathogenic avian H5N1 influenza virus in China. Methods Fecal and environmental samples were collected from a duck farm in Shandong Province.Samples were tested for type A influenza using real-time PCR,and the HA subtype of the positive samples was also determined.RNA was extracted from positive samples and was used for full-length genome sequencing.The complete viral genome was used in phylogenetic analyses and viruses were molecularly characterized. Results Real-time PCR results showed that one sample was positive for type A influenza and the HA subtype of that virus was determined to be H5.The strain was designated A/Duck/Shandong/1-14/2014（H5N1）.Phylogenetic analysis of the HA gene showed that it fell within the 2.3.2.1clineage.The PB2 gene came from a counterpart of the avian H9N2 influenza virus,but the remaining seven genes came from H5N1.The Shandong strain,the strain causing the first human infection with H5N1 in North America,and strains causing an outbreak of the avian influenza virus in Sanmenxia,Henan Province in January2015 were of the same genotype.However,no substitutions in key amino acid sites of this genotype were noted. Conclusions The Shandong strain belonged to 2.3.2.1c,a novel genotype that has recently been described.This genotype has been identified at different times（2014and 2015）,in different geographic regions（Beijing,Shandong Province,and Henan Province）,and in different hosts（poultry and wild birds）,suggesting that it might have achieved a certain level of fitness and continued to spread and evolve.Therefore,continued surveillance is warranted to monitor its further spread in a larger geographic region.