Table. Phylogenetic analysis of HA, NA, and M2 genes of influenza viruses A (H1N1) with different drug-resistance characteristics isolated in Hong Kong, January–June 2008*.
| Characteristics | No. isolates | HA clade | NA clade | M2 clade | Mutation |
|---|---|---|---|---|---|
| Oseltamivir resistant (n = 84) | |||||
| Amantadine susceptible | 81 | 2B† | 2B | 2B | H274Y in NA |
| Amantadine resistant | 1 | 2C† | 2B | 2C | H274Y in NA, S31N in M2 |
|
|
2 |
2C |
2C |
2C |
H274Y in NA, S31N in M2 |
| Oseltamivir susceptible (n = 37) | |||||
| Amantadine susceptible | 20 | 2B | 2B | 2B | None |
| Amantadine resistant | 14 | 2C | 2C | 2C | S31N in M2 |
| 3 | 2B | 2B | 2C | S31N in M2 |
*HA, hemagglutinin; NA, neuraminidase; M2, matrix. †Clade 2B or clade 2C indicates the gene specified has a nucleotide homology >99% to that of A/Brisbane/59/2007 or A/Hong Kong/2652/2006 virus, respectively.