However, the pure NA-H275Y + PA-I38T Group I infected ferrets (where the RF1 viral infection became a mixture with WT virus, potentially as a result of contamination) revealed evidence of reassortment with the WT virus, given the RF2 shed pure virus with a WT sequence on the PA and NA genes (PA-I38, PA-P325, NA-H275), and double mutant virus associated sequence on the HA and PB1 genes (HA-A204 and PB1-Y129). The gene discussed is XK; the disease is viral infectious disease.