Hong Kong influenza infection in swine: experimental and field observations.

The recovery of influenzaviruses indistinguishable from A/Hong Kong/68 virus from pigs in Taiwan in 1970 provided the first direct evidence of the interspecies transfer of influenzaviruses. Pigs were infected experimentally with that virus and transmitted the virus to pen mates. There was no evidence of A/Hong Kong/68 antibodies in serum collected from pigs prior to 1968. Such antibodies were detected in serum collected from pigs that lived during the period when Hong Kong influenza was epidemic in the human population.