Ge Z, Gu M, Cai T, et al. Phylogenetic tracing and biological characterization of a novel clade 188.8.131.52 reassortant of H5N6 subtype avian influenza virus in China. Transbound Emerg Dis. 2020;10.1111/tbed.13736
In recent years in China, clade 184.108.40.206 H5N6 plus clade 220.127.116.11 H5N1 subtype highly pathogenic avian influenza (HPAI) viruses have gradually become endemic in poultry, and their co-circulation could inevitably facilitate the gene reassortment between each other. During our routine surveillance in live poultry markets (LPMs) in Eastern China in 2017-2018, a novel reassortant H5N6 strain with the HA gene derived from clade 18.104.22.168 was isolated from the cloacal swabs of apparently healthy ducks. Phylogenetic tracing analysis indicated that another two clade 22.214.171.124 H5N1 strains with divergent lineages of PB1 gene and one clade 126.96.36.199 H5N6 isolate of the dominant genotype sharing spatio-temporal proximity were intimately involved in the generation of this rarely reported clade 188.8.131.52 H5N6 reassortant. Distinct with the other three HPAI H5 viruses showing moderate virulence in mice, the H5N1 strain of the homologous internal-gene constellation against the clade 184.108.40.206 H5N6 reassortant was highly pathogenic which might probably attribute to the H3 subtype-derived PB1 gene. However, as compared to the clade 220.127.116.11 H5N6 ancestor, the clade 18.104.22.168 H5N6 reassortant displayed a broader tissue distribution and higher viral titers in mice, which could likely facilitate the viral maintenance and spread in nature. Therefore, our results highlight that continuous epidemiological survey of H5 subtype HPAI viruses in LPMs need to be strengthened to prevent the potential poultry or even public health threat of the novel reassortants from endemic viruses.
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