Continuing evolution of H9N2 influenza viruses endemic in poultry in southern China

摘要

Two distinct lineages of H9N2 influenza viruses represented by A/Chicken/Beijing/1/94 (Ck/Bei-like) and A/Quail /Hong Kong/G1/97 (G1-like) have become established and endemic in poultry in southern China. These established H9N2 lineages continue evolving to generate many different reassortant variants (or genotypes) and are causing sporadic cases of human infection.Studies of H9N2 viruses isolated from pigs in Hong Kong and Shandong Province have also raised the possibility of reassortment with human-like viruses from pigs. In addition, H9N2 viruses isolated beyond the late 1990s had preferential binding with alpha-2,6-NeuAcGal human-like receptors.These observations suggest that the H9N2 influenza viruses still have pandemic potential. Unlike highly pathogenic H5N1 influenza viruses that have been rarely detected in the live-poultry markets in Hong Kong since 2002, H9N2 viruses are still frequently isolated in our surveillance program. Therefore, we try to understand the continuing evolution of H9N2 viruses through genetic characterization and phylogenetic analyses of the viruses isolated in Hong Kong live-poultry markets from 2005 to 2009.