The Genesis and Evolution of H9N2 Influenza Viruses in Poultry from Southern China, 2000 to 2005

Abstract

H9N2 influenza viruses have become established in terrestrial poultry in different Asian countries over the last 2 decades. Our previous study demonstrated that quail harbor increasingly diverse novel H9N2 reassortants, including both Chicken/Beijing/1/94 (Ck/Bei-like) and Quail/Hong Kong/G1/97 (G1-like) viruses. However, since 1999, the genesis and evolution of H9N2 viruses in different types of poultry have not been investigated systematically. In the present study, H9N2 viruses isolated from chickens, ducks, and other minor poultry species were characterized genetically and antigenically. Our findings demonstrate that Ck/Bei-like H9N2 viruses have been introduced into many different types of poultry in southern China, including quail, partridges, chukar, pheasant, guinea fowl, and domestic ducks, while G1-like viruses were commonly detected in quail, less frequently detected in other minor poultry species, and not detected in chickens and ducks. Genetic analysis revealed 35 genotypes of H9N2 viruses, including 14 novel genotypes that have not been recognized before. Our results also suggested that two-way interspecies transmission exists between different types of poultry. Our study demonstrates that the long-term cocirculation of multiple virus lineages (e.g., H5N1 and H9N2 viruses) in different types of poultry has facilitated the frequent reassortment events that are mostly responsible for the current great genetic diversity in H9N2 and H5N1 influenza viruses in this region. This situation favors the emergence of influenza viruses with pandemic potential.

Genetic analysis of polymerase complex (PA, PB1 and PB2) genes of H9N2 avian influenza viruses from Iran (1999 to 2009)

“…Previous and A/quail/Hong Kong/G1/97 (G1-like) [22] . As reported by Xu et al (2007), our result also showed that Polymerase complex genes of H9N2 viruses formed different sublineages including G1-like , Ck/ Beijing -like( or Y280-like) , three duck lineages (Dk1, Dk2,Dk3) and unknown avian [25] .…”

Evolution of the H9N2 influenza genotype that facilitated the genesis of the novel H7N9 virus

“…Phylogenetic trees were automatically partitioned into clusters (24) using a 20th percentile cutoff. Clades were then manually merged, if necessary, based on the branching posterior and reported classification (19,20,25). In each tree of eight segments, most of the 2010-2013 viruses belonged to the same clade ( Fig.…”

“…Briefly, clades with median root-to-tip distances equal to or less than 20% of the median root-to-tip distances of all clades in the tree were selected as clusters. Clades were then manually merged, if necessary, based on the branching posterior and reported classification (19,20,25). Each clade was assigned a unique clade ID.…”

PA-X is a virulence factor in avian H9N2 influenza virus

“…H9N2 influenza viruses have been widely reported to infect mammals, including pigs and humans (Abolnik et al, 2010;Butt et al, 2010;Cong et al, 2007;Sun et al, 2010;Xu et al, 2007); there is evidence that a large number of people have been infected with H9N2 viruses, in particular poultry workers (Coman et al, 2013;Jia et al, 2009;Wang et al, 2009). H9N2 virus infections in humans showed typical human flu-like symptoms, which can easily go undetected or unreported (Butt et al, 2005;Lin et al, 2000).…”