Analysis of nucleotide sequence and phylogeny on HA1 gene of influenza B viruses isolat- ed in Hebei

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