Perhaps it is not surprising, therefore, that the sialic acid itself serves as the major point of contact with the glycan-binding viral attachment protein in all cases where structural information of sufficient resolution is available [8, 13, [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] .