Neuraminidases (NA, sialidases, EC 3.2.1.18) cleave terminal sialic acid residues from oligosaccharides, glycoproteins and glycolipids. These enzymes are expressed in some viruses, bacteria, protozoa and fungi, and are ubiquitous in the deuterostomate branch of the Metazoa. Neuraminidases have been suggested to play a role in the pathogenicity of certain microorganisms, particularly, when enhanced expression of neuraminidases coincides with higher infectivity or when the severity of an infection is correlated with elevated concentrations of free N-acetylneuraminic acid[[1]. Furthermore, NA has been demonstrated to promote virus invasion into airways through the removal of decoy receptors on mucins, cilia, and cellular glycocalyx, physiologically impeding virus access to target cells. Influenza represents a major public health threat worldwide. And neuraminidase inhibitors represent an important measure to reduce the risk of influenza-related complications among high-risk patients developing influenza infection[2].