Variants of influenza A viruses resistant to amantadine possessed amino acid substitutions at one of 5 residues (26, 27, 30, 31, and 34) in the M2 protein [24, 25] . Sequence analysis did not reveal any mutations associated with resistance to amantadine. Thus all A/duck/Tuva/01/ 06 is potentially sensitive to this class of antiviral agents. Amino acid residues 119, 274, 292 and 294 in the NA protein (numbering according to the HA of H2 subtype) are crucial for the sensitivity of influenza A viruses to neuraminidase inhibitors [26] ; substitution H 274 →Y in the NA conferred resistance to Oseltamivir was observed in clinical H5N1 isolates [25, 26] . Sequence comparison of the NA protein of A/duck/Tuva/01/06 aligned with the NA of N2 subtype of A/Wuhan/359/95 (H3N2) influenza virus showed phenotype potentially sensitive to neuraminidase inhibitors.