| Abstract: | Investigations indicated that the epidemic upsurge of influenza morbidity in the 2005-2006 season in Russia was caused by the active circulation of influenza viruses A and B. The Center for Ecology and Epidemiology of Influenza, D. I. Ivanovsky Institute of Virology, Russian Academy of Medical Sciences, studied 182 epidemic strains. A hundred and thirteen influenza viruses A(H3N2) were similar to the reference A/California/07/2004 or were its antigenic variants. Thirteen influenza virus A(H1N1) strains that were antigenic variants of the reference A/New Caledonia/20/99 were isolated in sporadic cases. Influenza viruses B were similar to B/Malaysia/2506/2004--lineage B/Victoria/2/87). All the strains were isolated in the MDCK cell culture. Comparative study of the sensitivity of the chicken embryo (CE) and MDCK isolation system to the 1999-2006 epidemic strains showed that CE tropism was least pronounced in influenza viruses A(H3N2). Analysis of the 2002-2006 strains demonstrated that influenza viruses A reacted actively with human erythrocytes of the blood groups 0(I) and A(II) and very slightly with chicken ones. Eighty-five influenza virus A(H3N2) strains from the 2005-2006 epidemic season were investigated for rimantadine susceptibility. The frequency of rimantadine-resistant influenza virus A(H3N2) strains was 38.0%. Studies of 79 paired sera from patients revealed a rise of antibodies to influenza viruses A(H3N2) and B in 25.9-33.3 and 20.7-23.8% of cases, respectively. There was an increase in antibodies to influenza viruses A and B in the sera collected from donors in Moscow and its region in September 2005 to June 2006. |
