The paper gives the results of sequence analysis of 150 positive samples in real-time RT-PCR, including 47 autopsy materials from patients (including 10 pregnant women), who died from fatal pneumonia mainly in November-December 2009, in whom the lifetime etiological diagnosis had not been made and hence no early etiotropic therapy performed. 70% of the primary materials from the deceased patients were found to have pandemic influenza A(H1N1) v mutants in the lung tissue with D222G (15%), D222N (15%), D222E (2%) substitutions, as well as a mixture of mutants (38%). Nasopharyngeal lavages from 3 Chukotka deceased patients exhibited only consensus (nonmutant) D222 virus variants; there was a mixture of consensus and mutant virus variants in the trachea and a mixture of mutant ones in the lung. Preliminary data from the study of the interaction of the hemagglutinin of two strains having D222G and D222N mutations with 9 oligosaccharides imitating the variants of cell receptors for influenza A virus suggest that there is a double receptor specificity for alpha2'-3' and alpha2'-6'-sialosides with a preponderance of alpha2'-3'-specificity. Further spread of the mutants that have acquired a high virulence and preserved their capacity for the respiratory route of human infection may lead to the situation similar to that seen in the 1918-1919 pandemic. Another scenario for evolution of the virus is to preserve its receptor specificity for alpha2'-3'-sialosides and high virulence with losses of alpha2'-6' specificity and capacity for aerosol transmission, by damping the pandemic.