influenza A(H1N1)pdm viruses in patients who were admitted to the ICU. Viruses

In this study, we used NGS analysis to identify the characteristic amino acid substitutions of influenza A(H1N1)pdm09 virus in 9 patients who were admitted to the intensive care unit. In addition, within-host genetic diversity of influenza A(H1N1)pdm09 virus was analyzed using the whole-genome viral sequences from the upper and lower respiratory tracts of the patients. In this study, a higher rates of patients had the HA-D222G/N substitution than in previous studies. Furthermore, the substitution was detected only in the samples from the lower respiratory tract. Therefore, it is important to investigate influenza A(H1N1)pdm09 virus populations using multiple paired samples from the upper and lower respiratory tract to avoid overlooking potentially important substitutions, especially in patients with severe disease.