Table 1.
Full catalogue of characteristic sites for human-to-human transmission of influenza A identified for the PB2 protein. For each site, we show the position in the alignment; the characteristic variants of the avian-to-avian (A2A) and human-to-human (H2H) transmissible sequences; the characteristic variants found in human H1N1 and HxN2 subtypes; the year when the human characteristic variant was first isolated; the conservation of the characteristic variants in avian and human sequences; and finally the percentage of human sequences that exhibit avian variant. Sites where human characteristic variants were present in 1918 are highlighted in bold type.
| Position | Char. Variants | 1st Human isolate | Conservation | X-presence of A2A | ||
| A2A | H2H | A2A | H2H | |||
| 9 | DE | NT | 1933 | 98.57% | 99.33% | 0.49% |
| 44 | A | S | 1940 | 96.82% | 99.27% | 0.61% |
| 64 | M | T | 1933 | 97.29% | 99.58% | 0.30% |
| 81 | T | MV | 1933 | 97.93% | 99.27% | 0.30% |
| 105 | TA | VM | 1933 | 98.41% | 99.45% | 0.36% |
| 199 | A | S | 1918 | 99.47% | 99.76% | 0.24% |
| 271 | TI | A | 1940 | 98.59% | 99.51% | 0.37% |
| 292 | IV | T | 1940 | 95.54% | 99.15% | 0.67% |
| 368 | R | K | 1940 | 98.12% | 99.33% | 0.67% |
| 475 | L | M | 1918 | 99.66% | 99.76% | 0.24% |
| 567 | DE | N | 1918 | 98.28% | 99.39% | 0.55% |
| 588 | AV | I | 1940 | 98.45% | 99.63% | 0.31% |
| 613 | VA | T | 1940 | 98.28% | 96.82% | 0.61% |
| 627 | E | K | 1918 | 99.31% | 99.76% | 0.12% |
| 661 | A | T | 1933 | 86.72% | 99.39% | 0.43% |
| 674 | AS | T | 1933 | 95.69% | 99.63% | 0.18% |
| 702 | K | R | 1918 | 89.70% | 99.39% | 0.49% |