Guanidine-based poly (amido-amine) polymers of formula (I) : wherein n is an integer between 3 and 400 R1 is H, C1-6 alkyl or taken together with the N atoms to which is bound and R2 is a piperazinic ring R2 is C2-6 alkylen C5-6 cycloalkylen CH-COOH, CH-COOR, wherein R is C1-4 alkyl, phenyl or benzyl R3 is - (CH2) p-HN-C (NH2) =NH, wherein p is an integer 1 to 6 for use as antiviral agents in the prevention and/or treatment of viral infections in a mammal, preferably a human subject.