Highly Pathogenic Avian Influenza A(H5N8) Viruses Reintroduced into South Korea by Migratory Waterfowl, 2014-2015

Abstract

Highly pathogenic avian influenza A(H5N8) viruses were isolated from migratory waterfowl in South Korea during fall 2014-winter 2015, a recurrence after initial introduction in winter 2014. These reappeared viruses were phylogenetically distinct from isolates circulating in poultry farms in South Korea.

Keywords: H5N8; South Korea; highly pathogenic avian influenza virus; influenza; phylogenetic analysis; viruses; wild waterfowl.

Figure 1

Median-joining phylogenetic network of highly pathogenic avian influenza A(H5N8) viruse isolates identified in South Korea during 2014–2015 showing relationships with other virus isolates. The median-joining network was constructed from the hemagglutinin gene and includes all the most parsimonious trees linking the sequences. Each unique sequence is represented by a circle sized relative to its frequency in the dataset. Branch length is proportional to the number of mutations. Isolates are colored according to the origin of the sample: red inner circle, poultry farm isolates; yellow inner circle, wild bird isolates. Red asterisks indicate isolates from South Korea and blue asterisks indicate isolates from Japan identified during December 2014–February 2015.

Figure 2

Temporally structured maximum clade credibility phylogenetic tree (years shown on the horizontal axis) of the hemagglutinin gene of highly pathogenic avian influenza (H5 clade 2.3.4.4) viruses. Yellow, group A; green, group B. Branches of group A are colored according to the origin of the sample: purple, isolates from poultry farms (South Korea); blue-green, icA2 (North America, Japan); green, icA1 (Europe, South Korea, Japan); red, icA3 (South Korea, Japan).