Antigenic structure and biological characteristics of influenza strains isolated in the USSR during the 1974/75 epidemic.

Antigenic analysis of strains isolated in the USSR during the epidemic in 1974/1975 showed differences in the hemagglutination inhibition test and in neuramidase activity with antisera against three reference strains. Strains isolated in a later period of the epidemic were classified into subgroup A/Port Chalmers/1/73. Nearly all strains were effective inducers of interferon and were susceptible to this inhibitor of virus replication.