Introduction of H5N1 to the Americas by Migratory Waterfowl Unlikely

Migratory waterfowl are the natural reservoirs for influenza A viruses. Although most such viruses are of low pathogenicity, recombination of genes from different strains occasionally creates viruses that are highly pathogenic for birds, humans, or both. The H1N1 virus underlying the 1918 influenza pandemic is the most dramatic example to date. Believing that a new, major influenza pandemic is long overdue, experts are carefully watching the highly pathogenic H5N1 virus.

Overlaps in the pathways of migratory waterfowl between eastern Eurasia and Alaska and between Europe and eastern North America could allow H5N1 influenza strains to be spread to the Americas. To determine how often new influenza virus genes are introduced in this manner, sc…