A new subtype of avian influenzavirus: antigenic characteristics of envelope antigens

The haemagglutination and neuraminidase antigens of three influenza A isolates from ducks in the Ukraine were compared with those of a collection of reference strains of influenza A virus. Duck/Ukraine/1/60 virus contained haemagglutinin related to that of duck/England/56 while its neuraminidase was related to that of turkey/Wisconsin/68 virus and the human A/Hong Kong/1/68 virus. Duck/Ukraine/2/60 and duck/Ukraine/1/63 were themselves closely related. They contained haemagglutinin antigens unrelated to the six haemagglutinin subtypes previously described for avian influenzaviruses and it is suggested that they should be classified as belonging to haemagglutinin subtype Hav7. The neuraminidase antigens of these isolates were antigenically related to those of a number of other avian influenza viruses isolated in England, Canada, and Italy and to that of A/equine/ Miami/63 virus.