Clinically important neuraminidase mutations conferring resistance to neuraminidase inhibitors

NA: neuraminidase.
* Numbers indicate the position of the substituted residue according to specific viral subtype sequence.
¶ World Health Organization susceptibility categories: S: susceptibility or normal inhibition (<10-fold increase in inhibition for influenza A; ≤5-fold increase in inhibition for influenza B); RI: reduced inhibition (between 10- and 100-fold increase in inhibition for influenza A; between 5- and 50-fold increase in inhibition for influenza B); HRI: highly reduced inhibition (>100-fold increase in inhibition for influenza A; >50-fold increase in inhibition for influenza B).