19 The D225N mutation has also been reported to affect receptor binding of the HA whereas it also results in reduced susceptibility to neuraminidase (NA), 20 and has previously also been reported to be associated with serious influenza illness requiring hospitalisation or death. 21 The authors believed that the chance of person to person transmission in India with high population density created opportunities for the strain to sustain and they become dominant. This evidence concerns the gene XK and influenza.