The next major event in nature was the massive die-off of waterfowl at Qinghai Lake in China. [39] [40] [41] Four different genotypes of H5N1 HPAI viruses co-circulated in the waterfowl there; one of these became dominant and spread westward to India, Europe, and Africa. Notable features of the dominant Qinghai Lake H5N1 HPAI isolates were the acquisition of a lys627 mutation in the PB2 gene and the absence of pathogenicity in mallard ducks. 42 The lys627 mutation has been found to be associated with pathogenicity in mammalian species, 43, 44 suggesting that it may have been generated while the virus was replicating in a mammal. The virus was likely transmitted from domestic ducks to wild ducks en route to Qinghai Lake.