The FLUBV NA protein is similar to the FLUAV NA protein and performs comparable functions for the virus’ replication cycle [57,58,59], including removing sialic acids from respiratory mucins and cilia to allow for efficient movement within the respiratory tract, catalyzing the cleavage of terminal SAs from virus receptors to facilitate viral fusion, and cleaving glycosidic linkages between terminal sialic resides from glycoproteins on infected host cells and newly formed viral particles, thereby promoting the infection process [12,58,60,61]. Here, XK is linked to infection.