Characterization of a swine-like reassortant H1N2 influenza virus isolated from a wild duck in the United States.

An H1N2 influenza virus (A/Duck/North Carolina/91347/01) (Dk/NC) was isolated from a wild duck in the United States in 2001. Genetic analyses showed that this duck virus has the same human/classical swine/avian reassortant genotype as the H1N2 viruses that have been isolated from pigs and turkeys in the US since 1999. Phylogenetic analyses of each gene segment further confirmed that the Dk/NC virus is closely related to the domestic animal H1N2 isolates. In particular, Dk/NC is most closely related to a swine H1N2 virus also isolated in North Carolina. These two viruses and a phylogenetically-defined subset of additional swine H1N2 viruses share a common mutation in the Sb antigenic site on the hemagglutinin protein. The recovery of Dk/NC from a wild bird raises concerns for further widespread distribution of these H1N2 viruses via waterfowl migration.