对１９８９年春在河北保定分离的两株乙型流感病毒进行了抗原性、ＨＡ＿１基因序列和种系发生分析，与不同期的国内外代表株比较结果表明，自１９８８年以来乙型流感病毒变异较快，Ｂ／河北／５３／８９株的ＨＡ＿１基因序列与Ｂ／挪威／１／８５株相比，其氨基酸的同源性为９４．５２％，与同期的Ｂ／香港／２０／８９株同源性为９７．１２％。种系发生分析结果，从１９８８至１９８９年乙型流感病毒出现了５个支系，同期在保定分离的两株病毒，在同源替代中分别属于两个支系。日本国基本每隔两年出现一次乙型流感的流行优势型，其发生频度与甲型流感相似。国内少见乙型的流行优势型，可能和使用的分离病毒材料有关，日本用ＭＤＣＫ细胞比国内用鸡胚对乙型流感病毒的分离阳性率高。

In the spring of 1989,two influenza B viruses were isolated in Baoding, Hebei.The re-sults of antigenic,HA_1 gene nucleotide sequence and phylogenetic analysis of the two isolatesin comparison with other reported strains of influenza B viruses revealed that the antigenity of influenza B viruses had varied at a higher speed since 1988.The amino acid sequence ofHA_1 subunit of B/Hebei/53/89 exhibited 94.52% homology with that of B/Norway/1/85,and 97.12%with that of B/Hong Kong/20/89.The synonymous substitution analysis of theinfluenza B viruses HA_1 gene indicated that these HA_1 gene can be segregated into 5 lineagesand viruses evolved rapidly since 1988.The two viruses isolated in Hebei belonged to two lin-eages. Influenza B viruses usually become dominant at interval of two years in Japan. with e-qual frequency as influenza A viruses. However,influenza B viruses had not been reporteddominant in China. We believed that this was attributed to the methods used for the isolationof influenza B viruses:the pos