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

Twenty-two strains of influenza A virus isolated from caged birds which had been imported into Japan from India and Thailand and had died druing 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 hemagglutining and were related to A/duck/Czech/56 [Hav 4 Nav 1]. All strains contained Neq2 neuraminidase that was closely related to that fo 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 Naq2 and those in the second group were Hav4 Neq2; both group of viruses showed antigenic drift from the prototype strains.