Additionally, the clade 2.3.4.4c H5N6 HPAIVs caused infections of mammals including humans, and most showed a single amino acid (133, H3 numbering) deletion in the receptor-binding site of hemagglutinin (HA) and an 11 amino acid deletion in the stalk of neuraminidase (NA), reflecting a balance of HA and NA activity and adaptation to chickens [7]. Here, XK is linked to infection.