The analysis of non-structural protein 1 (NS1) which also could be contributed for high virulence of H5N1 viruses revealed deletion of 5 amino acids similar to those in H5N1 viruses of genotype Z which could be contributed to increased expression of TNF-α and IP-10 protein in primary human macrophages [18] . A/duck/Tuva/01/06 con-tained Glu 92 in the NS1 and contained "avian-like" PDZdomain ligand ESEV [19] . It was shown that the most recent H5N1 strains isolated in Southeast Asia were resistant to amantadine and rimantadine; antiviral drugs targeted the M2 ion channels of influenza A viruses [20, 21] . It was also reported about Oseltamivir resistant H5N1 viruses isolation from humans [22, 23] . To determine the potential sensitivity of studied H5N1 viruses to these antivirals, amino acid sequences of the M2 and NA proteins were analyzed.