Transmission of Eurasian avian H2 influenza virus to shorebirds in North America

Influenza A virus of the H2 subtype caused a serious pandemic in 1957 and m ay cause similar outbreaks in the future. To assess the evolution and the a ntigenic relationships of avian influenza H2 viruses, we sequenced the haem agglutinin (HA) genes of H2 isolates from shorebirds, ducks and poultry in North America and derived a phylogenetic tree to establish their interrelat ionships. This analysis confirmed the divergence of H2 HA into two geograph ical lineages, American and Eurasian. One group of viruses isolated from sh orebirds in North America had HA belonging to the Eurasian lineage, indicat ing an interregional transmission of the H2 gene. Characterization of HA wi th a monoclonal antibody panel revealed that the antigenicity of the Delawa re strains differed from the other avian strains analysed. The data emphasi zes the importance of avian influenza surveillance.