N(nt) N(aa) Codon Position Nucleotide HA0 Domain 1 1 1 100 A signal peptide 2 2 1 10 U signal peptide 3 3 1 1 G signal peptide 4 848 283 10 U HA1 5 1040 347 10 U HA2 6 1054 352 100 G HA2 7 1061 354 10 U HA2 8 1066 356 100 G HA2 9 1073 358 10 G HA2 10 1078 360 100 G HA2 11 1085 362 10 U HA2 12 1094 365 10 G HA2 13 1096 366 100 U HA2 14 1123 375 100 G HA2 15 1138 380 100 G HA2 16 1141 381 100 G HA2 17 1153 385 100 A HA2 18 1199 400 10 U HA2 19 1316 439 10 A HA2 20 1334 445 10 U HA2 21 1343 448 10 A HA2 22 1399 467 100 A HA2 23 1418 473 10 A HA2 24 1426 476 100 G HA2 25 1442 481 10 G HA2 26 1457 486 10 A HA2 27 1535 512 10 U HA2 28 1592 531 10 U HA2 29 1628 543 10 U HA2 30 1645 549 100 G HA2 31 1655 552 10 U HA2 32 1657 553 100 U HA2 33 1658 553 10 G HA2 34 1659 553 1 G HA2 35 1663 555 100 U HA2 36 1664 555 10 G HA2 37 1679 560 10 U HA2 38 1685 562 10 G HA2 39 1694 565 10 G HA2 40 1699   100 U TER

Table 2: HA Nucleotide Positions with Zero Hamming Distance Between All H1N1, H3N2 and H6N1 Sequence Pairs. Nucleotide (nt) and amino acid (aa) positions are identified by number (N) in the second and third columns. Codon positions are designated as decimation frame first codon position (100), second codon position (010) and third codon position (001) in the fourth column. The termination codon is designated as TER in row 40. The HA nucleotides are identified in the mRNA representation.