Table 1.
Phylogenetic classification based on the HA of A(H1N1)pdm09 viruses isolated during the 2018–2019 and 2019–2020 influenza seasons.
| Influenza Season | Amino Acid Substitution in HA |
Subclade | Total | |||||
|---|---|---|---|---|---|---|---|---|
| 6B.1A | 183P-2 | 183P-4 | 183P-5 | 183P-5A | 183P-7 | |||
| 2018–2019 | N156K | 0 | 8 (7.6%) | 0 | 0 | 1 (1.0%) | 0 | 9 (8.6%) |
| D187A and Q189E | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
| N156S, D187A, and Q189E | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
| Others | 1 (1.0%) | 23 (21.9%) | 4 (3.8%) | 4 (3.8%) | 62 (59.0%) | 2 (1.9%) | 96 (91.4%) | |
| Total | 1 (1.0%) | 31 (29.5%) | 4 (3.8%) | 4 (3.8%) | 63 (60.0%) | 2 (1.9%) | 105 | |
| 2019–2020 | N156K | 0 | 0 | 0 | 0 | 22 (10.1%) | 0 | 22 (10.1%) |
| D187A and Q189E | 0 | 0 | 0 | 0 | 195 (89.4%) | 0 | 195 (89.4%) | |
| N156S, D187A, and Q189E | 0 | 0 | 0 | 0 | 1 (0.5%) | 0 | 1 (0.5%) | |
| Others | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
| Total | 0 | 0 | 0 | 0 | 218 (100%) | 0 | 218 | |