[Variability and prevalence characteristics of Influenza A virus (H1N1) in period 1990-1998].

Circulation of influenza A(H1N1) viruses in Russia and CIS countries had a wave-like pattern with period of silence in 1990-1995 and activation in 1995-1998, when these viruses were isolated together with A(H3N2) and B viruses. Antigenic drift of epidemic strains' hemagglutinin (HA) was directed to alteration of HA in reference strains A/Texas/36/91, A/Johannesburg/82/96, and A/Beijing/262/95. A/Moscow/17/98 strain similar to A/Beijing/262/95 was isolated on MDCK cells for the first time in European Russia. This means that A/Beijing/262/95 (H1N1) spread sporadically in the country at that time. Comparative analysis of HA thermosensitivity of influenza A(H1N1) strains of 1977-1998 showed a tendency to increase of their thermal stability. The sensitivity of erythrocytes of different animals to A(H1N1) strains isolated during the same epidemic season was different. Differences in amino acid sequences of epidemic strains' HA varied from 5 to 14 sites in comparison with the reference strains, depending on the reference strain and year of isolation.