[Comparative study on the properties of influenza B viruses isolated in 1959-1974]

The biological properties and antigenic structure of the following influenza B virus strains were compared: Moscow/Likh/59, Moscow/106/62, Moscow/1/66, Hong Kong/5/72, Yamagata/73 and USSR/01/4. The influenza B virus strains isolated in 1972-1974 differed by hemagglutinin from those isolated in 1959-1966. The variability of hemagglutinin correlated with that of neuraminidase. Yamagata/73 virus occupied a special position both with regard to the structure of surface antigens and to some other biological properties. Therefore, the possibility of occurrence in the USSR of virus strains similar to Yamagata/73 cannot be ruled out.