XK and influenza: Although variants resistant to NA and PA inhibitors are much less than M2 inhibitors, the high variability of influenza viruses, such as seasonal H1N1 viruses carrying the H275Y, H275Y and I38T mutations [5] and the H7N9 virus carrying the R294K mutation [6], enables the rapid evolution of antiviral resistance to drugs, underscoring the urgent need for the development of new anti-influenza drugs.