Highly Pathogenic Avian Influenza A(H5N8) Virus in Wild Migratory Birds, Qinghai Lake, China

Abstract

In May 2016, a highly pathogenic avian influenza A(H5N8) virus strain caused deaths among 3 species of wild migratory birds in Qinghai Lake, China. Genetic analysis showed that the novel reassortant virus belongs to group B H5N8 viruses and that the reassortment events likely occurred in early 2016.

Keywords: China; H5N8; HPAI; Highly pathogenic avian influenza virus; Qinghai Lake; bird diseases; influenza; influenza in birds; phylogenetic analysis; reassortment; viruses; wild aquatic birds; wild migratory birds.

Figure 1

Phylogenetic analyses of 594 hemagglutinin (HA) sequences (1,704 nt) from clade 2.3.4.4 H5 influenza viruses. A) HA-coding sequence subtree from maximum-likelihood phylogenetic analysis of the clade 2.3.4.4 H5 viruses. Colored nodes: blue, Qinghai Lake H5N8 strains (this study); red, Ubsu-Nur Lake H5N8 strains. B) Maximum-likelihood phylogenetic tree of the clade 2.3.4.4 HA-coding sequences, rooted with A/Goose/Guangdong/1/96(H5N1). Scale bars indicate nucleotide substitutions per site. C) Median-joining phylogenetic network of the HA-coding gene sequences, including the most parsimonious trees linking the sequences. To simplify the network, nodes with only one sequence are not shown. Network branch lengths are proportional to the numbers of mutations. icA, intercontinental group A; icA1, intercontinental subgroup A1; icA2, intercontinental subgroup A2; icA3, intercontinental subgroup A3; icB1, intracontinental subgroup B1.

Figure 2

Hypothetical evolutionary pathway of influenza (H5N8) viruses from Qinghai Lake, China. Gene segments are colored according to their origins. Dashed virions indicate unidentified viruses. HA, hemagglutinin; LPAI, low pathogenicity avian influenza; MP, matrix protein; NA, neuraminidase; NP, nucleoprotein; NS, nonstructural protein; PA, acidic polymerase; PB, polymerase basic.