Reappearance of H1N1 influenza virus in man: evidence for the persistence of the virus in domestic chickens.

Serological studies on domestic poultry originating from China and Hong Kong suggest that the H1N1 virus may have persisted in domestic chickens prior to its reappearance in man in 1977. Experimental infection of young, local strains of poultry provided equivocal evidence that 4-day-old chickens could be infected; virus was not recovered from infected 1-month-old chickens.