Evolution and spatial dissemination of the highly pathogenic Asian H5 avian influenza viruses

Abstract

After emerging in 1996, the Asian highly pathogenic avian H5Nx influenza viruses had spread to more than sixty countries across Asia, Europe, and Africa through three major transmission waves by 2006. Phylogenetic analysis of all H5 influenza virus sequence data in our long-term surveillance in southern China revealed that the virus was widespread and enzootic in China, continuously developing into different clades and reassortant variants, some of which disseminated to other regions and became enzootic. This indicates that continuous circulation of H5 viruses in China is not only a local risk factor, but also poses a broader threat to birds and humans in other regions. In late 2014, clade 2.3.4.4 of H5Nx viruses emerged and caused sporadic human infections in China and outbreaks in poultry in Eurasia and spread to North America, the first-time Asian highly pathogenic H5 viruses had been detected there. To ascertain how the Asian H5Nx influenza viruses evolved into the wide-spread clade 2.3.4.4 viruses, over 3,000 H5 avian viruses isolated from 2009 to 2015 have been sequenced. I wish to use more sophisticated phylodynamics analysis on our large genomic sequence datasets of H5Nx viruses to examine the emergence of new wide-spreading 2.3.4.4 clade of global concern.