3 - PB2, PB1 and PA polymerase genes of 2 virus strains, A / Duck / VietNam / QT801/2011 (H5N1) and A / Duck / VietNam / QT802/2011 (H5N1) (clade 2.3.2.1), with 2 virus strains A / Duck / VietNam / NA72/2007 (H5N1) and A / Duck / VietNam / NA114/202007 (H5N1) (clade 2.3.4.3), derived from the V genotype of the A / H5N1 influenza virus genome source, that generated in China during 2004 - 2006 period.