The follow-up study of swine and Hong Kong influenza virus infection among Japanese hogs.

Pigs in Miyagi Prefecture, Japan were examined for swine (Hssw1N1) and Hong Kong (H3N2) influenza virus infection by serological tests. The results obtained revealed that a swine influenza was prevalent with relatively high positive ratios throughout that time, and that the Hong Kong influenza virus closely related to a recent human epidemic strain, A/Yamanashi/2/77, also persisted, corresponding to a human endemic. These epidemiological findings strongly suggested the possibility of direct transmission of Hong Kong virus from humans to pigs and vice versa.