Genetic Relationship between an Influenza A and a B Virus

The base sequence homology between all eight 32P-labelled RNA segments of fowl plague virus (FPV) and the complementary RNA (cRNA) of an influenza B virus (B-Mass), and between segment 8 of virus N and the cRNA of the same influenza B strain has been determined. All segments of FPV and segment 8 of virus N show a significant base sequence homology, ranging from 18 to 50% suggesting that influenza A and B viruses have a common ancestor. The conserved regions in segments 4, 6, and 8 of the influenza A strains are identical to corresponding regions of the influenza B virus tested.