Novel branched sialo-sugar molecules and antiviral agents using the same

A novel branched sialo-sugar molecule represented by the following formula (I) which is a substance which responds to a variation in the host range of an influenza virus or a variation in antigenicity and is useful as a drug or an adsorbent in a virus removal filter or the like capable of preventing the infection with a type A influenza virus and a type B influenza virus originating in any animals including humans: (wherein NeuAc represents N-acetylneuraminic acid in which the hydroxyl group, the carboxyl group and the amido group may be chemically modified with a halogen group, an alkyl group or an acyl group, either the same group or separate groups, Hex represents hexose, HexNAc represents N-acetylhexosamine and R represents a substrate selected from among a hydrogen atom, a hydrocarbon chain, a sugar chain, a lipid, a protein and a synthetic polymer, R may have a substituent, and the linkage between N-acetylneuraminic acid and hexose may be either an O-glycoside linkage occurring in nature or a chemically converted linkage such as an S-glycoside or a Se-glycoside linkage) is provided.