Figure 1: Cumulative Hamming Distances (ΣD) Between Paired Influenza A Subtype Hemagglutinins. A. Data are shown for (H1N1, H3N2) sequence pairs (left),B. (H1N1, H6N1) sequence pairs (middle) and C. (H3N2, H6N1) sequence pairs (right). Black lines (observed ΣD); red dashed lines (approximations by summed single binomial function).