Genetically Different Highly Pathogenic Avian Influenza A(H5N1) Viruses in West Africa, 2015

Abstract

To trace the evolution of highly pathogenic influenza A(H5N1) virus in West Africa, we sequenced genomes of 43 viruses collected during 2015 from poultry and wild birds in 5 countries. We found 2 co-circulating genetic groups within clade 2.3.2.1c. Mutations that may increase adaptation to mammals raise concern over possible risk for humans.

Keywords: Africa; H5N1 subtype; HPAI; Influenza A virus; West Africa; genetic groups; highly pathogenic avian influenza; phylogeny; respiratory infections; viruses.

Figure

Maximum-likelihood phylogenetic tree of the hemagglutinin gene segment of highly pathogenic avian influenza (H5N1) viruses from West Africa. Strain colors indicate country of collection (inset). The 2 identified groups (WA1 and WA2) are indicated by boxes (black and gray, respectively). Clades are indicated at right; sequences from the 2006–2008 epidemic (clade 2.2) in West Africa were used as an outgroup. Numbers at the nodes represent bootstrap values >60%, obtained through a nonparametric bootstrap analysis that used 100 replicates. Scale bar indicates nucleotide substitutions per site.