Antigenic andgenetic analyses ofinfluenza typeB viruses isolated inRussia, 1987-91

SUMMARY Fourinfluenza typeBvirusesisolated in Russiaduringperiodsofrelatively low(1987-8) or high (1990-1) influenza B activity were characterized antigenicallyusing a microneutralization assay. These isolates were antigenically similar tocontemporary reference strains from either oftwo separate lineages represented by B/Victoria/2/87 and B/Yamagata/16/88. The evolutionary relationships of the variable portion of the haemagglutinin (HA1) genes of these viruses were determined by comparison withinfluenza BHAIsequences previously obtained. The Isolate B/USSR/2/87, collected during the 1987-8 influenza season, was found to be closely related to viruses on the B/Victoria/2/87 lineage thatcirculated during the 1988-9 influenza season in the United States. Sequence analysis of the isolates from the 1990-1 influenza season demonstrated co-circulation of viruses from both the B/Victoria/2/87 and B/Yamagata/16/88 lineages in Russia, confirming the antigenic analysis.Significant levels of infection