[Properties of influenza virus strains causing the influenza epidemic in Moscow in 1972-3].

The antigenic and some biological properties of influenza virus strains isolated during 1972-1973 epidemic were studied. Altogether 114 strains were isolated from sick infants of the first months of life beginning from neonatality. The strains under study were found to have high adaptation and elution activity, to be highly sensitive to inhibitors and to produce polymorphous allantoic population in the adaptation period. The hemagglutinating and neuraminidase components were shown to be fairly closely related to those of the membrane of the reference A2/Hong Kong/1/68 strain (H3N2). At the same time, a low neutralizing activity of the antisera for this strain against Moscow strains of 1972-1973 in biological neutralization tests in chick embryos was observed, explaining very high susceptibility of the population to influenza type A infection in the winter of 1972-1973. The strains under study were antigenically homogenous and most closely related to the reference A2/England/42/72 (H3N2) strain.