XK and influenza: In the most recent 2013/14 Northern Hemisphere influenza season, a cluster of A(H1N1)pdm09 H275Y OR viruses that contained both the V241I and N369K PPMs plus an additional N386K NA mutation, was detected in Sapporo, Japan [53], during a period of the season where A(H1N1)pdm09 viruses contributed approximately 50% of the circulating influenza strains [54].