Influenza virus surveillance in migratory ducks and sentinel ducks at Poyang Lake, China

Abstract

INTRODUCTION: Aquatic birds are recognized as the natural reservoirs of the influenza A virus as all known subtypes (H1-H16, N1-N9) have been found in them. Phylogenetic analyses of influenza viruses found in other animals revealed that all were directly or indirectly derived from viruses resident in aquatic birds.1 However, the prevalence, movement, and evolutionary dynamics of influenza viruses in these avian hosts have not been well defined. Southern China was hypothesized to be an ‘epicenter’ for the generation of human pandemic influenza viruses as all major influenza pandemic viruses in the 20th century emerged from this region.2 The ecological background that facilitates the occurrence of these pandemic influenza strains has not been fully explored. In the past two decades, four lineages, belonging to H5N1, H9N2, and H6N1 viruses, have become established and long-term endemic in different types of poultry in this region.3–5 Some of these viruses were disseminated to many countries in Eurasia and Africa and have continued to cause sporadic human infection, posing a persistent pandemic threat to the world.6 In the mean time, the endemic influenza lineages have undergone extensive genetic reassortment events giving rise to many variants, dramatically increasing the genetic diversity of the influenza virus in this region …