The A/Brisbane/59/2007-like (H1N1) strains used were the oseltamivir-susceptible A/Québec/15230/08 (WT) and the oseltamivir-resistant A/Québec/15349/08 (NA-H275Y mutant). These clinical isolates were obtained from two distinct, untreated, immunocompetent patients during the 2007-2008 influenza season [22] . 