乙型流行性感冒病毒两大谱系的起源及其演变特征

测定1972－2000年间在中国分离并保存的乙型流行性感冒（流感）病毒一些毒株的HA1区核苷酸序列，结合GenBank中其它毒株的相关序列以及流行病学资料进行分析。结果提示，当前在世界上流行的乙型流感病毒两大谱系起源于20世纪70年代中期，而不是以前推测的60年代末，并且其中一个谱系起源于中国。结果还提示，乙型流感病毒的演变同时受到很强的正选择与负选择的作用，而以前人们认为选择对乙型流感病毒的演变作用甚微。还修正了乙型流感病毒变异速率的计算方法。

The Origin and Evolution of Two Genetic Lineages of Influenza B Virus

The nucleotide sequences of HA1 regions of some of the influenza B viruses isolated from 1972-2000 in China were tested and analyzed with the corresponding sequences of viruses previously reported as well as with their epidemic records.Results showed that the divergence of two main influenza B virus lineages began in mid-1970s,but not at the end of 1960s as previously suspected.Results also showed that the evolution of influenza B virus was under both strong positive selection and negative selection,which was contrary to previous reports.Calculation of the variation rate of influenza B virus was revised in this paper.