Diversity of influenza A virus subtypes isolated from domestic poultry in Hong Kong.

The second phase of a 2-year influenza virus surveillance programme of domestic avian species in Hong Kong (up to October 1977) yielded influenza A virus, Newcastle disease virus, and Hong Kong paramyxovirus, as well as unidentified haemagglutinating agents. These viruses were isolated from the trachea or cloaca of apparently healthy domestic ducks, geese, and chickens originating from China and Hong Kong. Twenty-five combinations of haemagglutinin and neuraminidase surface antigens were identified from the 136 influenza A viruses isolated. Eight of the combinations do not appear to have been previously reported — Hav3Nav2, Hav4Nav2, Hav4Nav4, Hav4Nav5, Hav4Neq1, Hav6Nav4, Hav6Nav6, and Hav9Nav1. The existence of such a diverse pool of influenza virus genetic information may play a role in the emergence of new human pandemic strains.