PERSISTENCE OF A 1930 SWINE INFLUENZA-A (H1N1) VIRUS IN QUEBEC

Two antigenically distinct H1N1 influenza A viruses were isolated duri ng an outbreak of respiratory disease in Quebec swine in 1990/91. Anal ysis of haemagglutinin and partial nucleoprotein sequences indicated t hat one was a variant of the swine H1N1 influenza virus circulating in the American Midwest whereas the other was very similar to virus isol ated from swine in 1930. The existence of this latter isolate supports the concept that influenza viruses can be maintained for long periods in swine, perhaps in geographically limited pockets. Serological evid ence indicates that these distinct strains continued to circulate wide ly in south-central Quebec until at least 1993.