Isolation and serological characterization of influenza A viruses from birds that were dead on arrival at Tokyo airport

Abstract

Twenty-two strains of influenza A virus were isolated from caged birds which had been imported into Japan from India and Thailand and had died during transportation to Tokyo. Serological tests divided these strains into two groups. Viruses in the first group contained Hav7 hemagglutinin and were related antigenically to A/duck/ Ukraine/1/63 [Hav7 Neq2]; viruses in the second group contained Hav4 hemagglutinin and were related to A/duck/Czech/56 (Hav4 Nav1]. All strains contained Neq2 neuraminidase that was closely related to that of A/equine/Miami/1/63 [Heq2 Neq2] and A/duck/Ukraine/1/63 [Hav7 Neq2]. It was concluded that the strains in the first group were Hav7 Neq2 and those in the second group were Hav4 Neq2; both groups of viruses showed antigenic drift from the prototype strains.