Strain Specific Complement-Fixation Differentiation of Influenza B Viruses Isolated in Tissue Culture.

Five strains of influenza B virus isolated in monkey kidney tissue cultures from 5 separate influenza outbreaks in the Midwest of the United States during the winter of 1961–62 were studied for antigenic variations. These strains were analyzed by the strain specific CF test and the standard HI test. The sera used were obtained during the acute and convalescent phases from 8 patients who had influenza B infection confirmed by virus isolation. The CF test could detect antigenic differences among influenza strains isolated from the same locale as well as from different geographic areas. These differences were not detectable by the HI test.