[Biological properties of strains of influenza virus that caused the epidemic of 1974-1975].

The biological features of the strains of influenza virus isolated in the 1974-1975 epidemic were compared with those of the strains which had circulated earlier. Most of the properties examined (toxicity for mice, sensitivity to gamma-inhibitors, thermostability of hemagglutinin and neuraminidase) in strains isolated in 1974-1975 did not differ from those in strains of previous epidemics. Clear-cut differences between the new and earlier strains were found in the studies of their chromatographic profiles.