Table 1. Frequency of mutations in the amino acid sequence of Hemagglutinin (HA) from the influenza A(H1N1)pdm09 virus.
| Collection date (year)1 | Number of sequences | Variant 1 (%) | Variant 2 (%) | Variant 3 (%) | Variant 4 (%) | ||
| S143G | S185T | A134T | D222E | P297S | E374K | ||
| 2009a | 1158 | 0.2 | 0.0 | 0.5 | 1.0 | 0.0 | 0.1 |
| 2009b | 1607 | 0.1 | 0.0 | 0.4 | 7.1 2 | 3.1 | 19.8 |
| 2010–2011 | 200 | 9.5 | 11.5 | 7.0 | 6.5 | 7.0 | 50.5 |
| 2011–2012 | 530 | 31.1 | 72.9 | 1.9 | 0.2 | 0.0 | 87.8 |
1
2009a represents sequences from January-June 2009 period; 2009b represents sequences from the July-December 2009 period.
2
Highest frequencies are shown in bold.