Multiple avian influenza infection: selection of a non-avid virus by a heterologous avian host.

Experimental infection of domestic fowl, ducks and geese with an influenza A virus (H7N2) isolated from a domestic duck showed that this virus was apathogenic for these poultry. A second virus (H6N2), also apathogenic and more 'non-avid' than any such isolates previously recognised in surveillance of domestic poultry in Hong Kong, was isolated from one goose after H7N2 shedding had ceased. This goose, in effect, acted as a selective isolation system for the H6N2 virus whose presence in the field isolate could not be detected in spite of multiple passage in embryonated eggs.