A PATTERN OF INFLUENZA VIRUS VARIATION

Abstract

100 strains of influenza A and influenza B viruses isolated at various times during the past 18 yrs. were tested by hemagglutination-inhibition tests with 6 antisera representative of 6 antigen complexes. The strains fall into 5 influenza A subgroups and 4 influenza B subgroups. The prevalence of the various subgroups appears to have been orderly and chronological: antigenic complexes which were dominant in previously isolated strains were obscured, or lacking, in more recently isolated strains, and complexes which were not apparent in the earlier strains were dominant in the more recent strains. Complexes which were dominant among the early strains have not recurred as dominant complexes among large groups of recently isolated strains. The compatibility of the data with the idea of biological selection in the immune host is discussed.