Genesis, Evolution and Prevalence of H5N6 Avian Influenza Viruses in China

Abstract

Constant surveillance of live poultry markets (LPMs) is currently the best way to predict and identify emerging avian influenza viruses (AIVs) that pose a potential threat to public health. Through surveillance of LPMs from 16 provinces and municipalities in China during 2014-2016, we identified 3,174 AIV-positive samples and isolated and sequenced 1,135 AIVs covering 31 subtypes. Our analysis shows that H5N6 has replaced H5N1 as one of the dominant AIV subtypes in southern China, especially in ducks. Phylogenetic analysis reveals that H5N6 arose from reassortments of H5 and H6N6 viruses, with the hemagglutinin and neuraminidase combinations being strongly lineage specific. H5N6 viruses constitute at least 34 distinct genotypes derived from various evolutionary pathways. Notably, genotype G1.2 virus, with internal genes from the chicken H9N2/H7N9 gene pool, was responsible for at least five human H5N6 infections. Our findings highlight H5N6 AIVs as potential threats to public health and agriculture.

An NS-segment exonic splicing enhancer regulates influenza A virus replication in mammalian cells

“…It is notable that human infections with H10N8 confirmed in China were caused only by H10N8 viruses, which contain NS-G540A; no human cases involving H10N8 virus without this mutation were found2456. Human infections with H5N6 virus occurred in China since 2014, with 11/16 (69%) of isolates characterized from human cases contain NS-G540A57. The mechanism underlying how this mutation in the here characterized NEP-ESE supports virus replication in mammalian cells should be further evaluated and future surveillance should also monitor for adaptive substitutions, which affect splicing of viral mRNAs.…”

Sialic acid receptors: focus on their role in influenza infection

“…These AIV are known to be the only subtype of clade 2.3.4.4 that is able to cross the host species barrier and infect humans with documented exposure to infected poultry. 60,61 Nonetheless, all H5 AIV isolated to date from birds, mammals, or humans show preferential binding to SAα2,3-linked receptors. [62][63][64][65][66][67] As described with the recent human H3N2 viruses, a progression on the type of SAα2,3-linked receptors recognized by the avian H5 has been observed, resulting from the high rate of antigenic and genetic diversity in H5N1 viruses.…”

Characterization of Highly Pathogenic Avian Influenza Virus A(H5N6), Japan, November 2016

“…Although the H5 HA genes of these viruses are closely related, the subtypes of their neuraminidase (NA) genes vary widely. These new H5 HPAIVs with NA genes of various subtypes, the so-called H5Nx viruses, have spread globally, most likely because of their host preference for waterfowl, similar to the previous H5N1 HPAIVs ( 2 – 4 ). During the winter season 2014–15, H5N8 HPAIVs were isolated from wild birds and chickens in western Japan ( 5 – 7 ).…”