[Significance of the heterogeneity of respiratory syncytial viral populations in the development of the epidemic process].

The manifestations of the epidemic process in respiratory syncytial (RS) virus infection induced by the strains of the infective agent, differing in their capacity for reproduction at 39 degrees and 37 degrees C and in their sensitivity to antibodies, were compared. The observation of children in a group (about 80 children simultaneously) with the systematic serological and virological examination of sick and healthy children was the main method in this investigation. The circulation of RS viruses with greater capacity for reproduction at 39 degrees and 37 degrees C and lesser sensitivity to antibodies, i.e. viruses with greater virulence, was accompanied by the increased intensity of manifestations of the epidemic process. An increase in the heterogeneity of RS virus populations isolated at the same period of observation was accompanied by the intensification of the epidemic process, which was manifested by increased morbidity rate and a higher level of contamination in children, an increase in the incidence of outbreaks and in the frequency of RS virus reinfection.