Volume 30, Number 7—July 2024
Dispatch
Multicountry Spread of Influenza A(H1N1)pdm09 Viruses with Reduced Oseltamivir Inhibition, May 2023–February 2024
Table 1
Influenza A(H1N1)pdm09 viruses with amino acid substitutions in neuraminidase that may affect inhibition by oseltamivir*
| NA substitution† | No. viruses with NA substitution | Viruses collected from countries (no. in each) |
|---|---|---|
| H275Y | 4 | Argentina (1),‡ Panama (1), USA (2) |
| I223V | 18 | Abu Dhabi (5), Bangladesh (5), Bahrain (2), Canada (1), Costa Rica (1), USA (4) |
| S247N | 15 | Abu Dhabi (2), Bhutan (3), Brazil (1), Canada (1), Hong Kong (1), Oman (1), USA (6) |
| I223V + S247N§ | 17 | Bangladesh (11), Hong Kong (1), Maldives (1), Niger (3), USA (1) |
*Next-generation sequencing–based virologic surveillance conducted at the Centers for Disease Control and Prevention, May 2023–February 2024. Summary of NA amino acid substitutions assessed for their effects on inhibition by NA inhibitors prepared by members of the World Health Organization Antiviral Working Group (5) was used as a reference for NA sequence analysis. A total of 2,039 NA sequences of influenza A(H1N1)pdm09 viruses (duplicate sequences excluded; n = 1,274 viruses collected from the United States and n = 765 from 38 other countries) were analyzed to screen for previously listed or suspected NA amino acid substitutions. Detailed information about those viruses is provided in Appendix Table 1). NA, neuraminidase. †According to a subtype-specific NA amino acid numbering system. ‡This virus also contains NA-S247N. Virus was not recovered in cell culture. §Combination of I223V + S247N was not reported previously.
1These authors contributed equally to this article.