From 2011 forward, our laboratory-based influenza antiviral resistance surveillance became broader than in previous years [7] because every current A(H1N1)pdm09-positive NPA received by our laboratory, from patients in 4 out of 5 regions of Brazil (498 cases in total: 163 from 2011 and 335 from 2012), was screened for H275Y and S247N mutations in the neuraminidase (NA) gene. Here, XK is linked to influenza.