Evolution and reassortment of influenza B virus during 1983-2013

Objective To study the evolution and reassortment of influenza B virus during 1983-2013.Methods Influenza B viruses with full genome sequence from 1983-2013 were downloaded from GenBank database for analysis.The reassortments of influenza B viruses were selected by Simplot program and were further analyzed and evaluated by MEGA program.Results In total 432 influenza B viruses had full genome sequences available for analysis,and among the 66 representative viruses,22 reassortant viruses were identified.Nine of the viruses were intra-lineage reassortants including 2 B/Vic-87 lineage viruses and 7 B/Yam-88 lineage viruses,while the other 13 were inter-lineage reassortants between B/Vic-87 and B/ Yam-88 lineages.Analysis with simplot program revealed similar result with MEGA program.Conclusions Reassortment of influenza B virus between different lineages or within the same lineage is frequent.Simplot program can be used for rapid screening of type B influenza reassortant virus. Key words: Influenza B virus ;  Genome ;  Reassortant virisos;  Evolution