A method for producing an antimicrobial and/or antiviral product, comprising, contacting at least one surface of a product with an antimicrobial and/or antiviral polymer, being a straight and/or branched polymer, comprising: nitrogen atoms, wherein the antimicrobial and/or antiviral polymer is a modified polymer of a precursor polymer, the precursor polymer having a median molecular weight in the range of from 25-2000 kDa, said precursor polymer being selected from the group consisting of polymers having the following formula I and copolymers thereof: wherein: R 1 and R 2 independently are selected from a straight or branched (C 1 -C 6) hydrocarbon chain; x is in the range of from 0 to 1; the precursor polymer of Formula I comprising two different types of building blocks, one containing secondary amines and one containing tertiary amines wherein the ratio between secondary and tertiary amines determines the degree of branching of the polymer and x, 0 ≤ x ≤ 1, and 1-x represents the portion (%/100) of the corresponding type of building block in the polymer; and wherein said precursor polymer is modified so that at least part of said nitrogen atoms are substituted with a substituent selected from the group consisting of straight or branched C 1 -C 20 -alkyl groups, and at least part of the nitrogen atoms in said precursor polymer are quaternized, said quaternized nitrogen atoms being substituted with a substituent selected from the group consisting of straight or branched C 4 -C 20 -alkyls, and where the antimicrobial and/or antiviral polymer is water-soluble, the degree of amine function substitution with a (C 1 -C 20) alkyl group for the antimicrobial and/or antiviral polymer varies with the polymer and the substituents used, and the degree of substitution is taken as the percentage of the amine-functions in the polymer, and the substitution degree is in the range of from 1 to 100%, and the antimicrobial and/or antiviral polymer is non-covalently adhered to the surface of the product avoiding special modification of the surface. nitrogen atoms, wherein the antimicrobial and/or antiviral polymer is a modified polymer of a precursor polymer, the precursor polymer having a median molecular weight in the range of from 25-2000 kDa, said precursor polymer being selected from the group consisting of polymers having the following formula I and copolymers thereof: R 1 and R 2 independently are selected from a straight or branched (C 1 -C 6) hydrocarbon chain; x is in the range of from 0 to 1; the precursor polymer of Formula I comprising two different types of building blocks, one containing secondary amines and one containing tertiary amines wherein the ratio between secondary and tertiary amines determines the degree of branching of the polymer and x, 0 ≤ x ≤ 1, and 1-x represents the portion (%/100) of the corresponding type of building block in the polymer; and wherein said precursor polymer is modified so that at least part of said nitrogen atoms are substituted with a substituent selected from the group consisting of straight or branched C 1 -C 20 -alkyl groups, and at least part of the nitrogen atoms in said precursor polymer are quaternized, said quaternized nitrogen atoms being substituted with a substituent selected from the group consisting of straight or branched C 4 -C 20 -alkyls, and where the antimicrobial and/or antiviral polymer is water-soluble, the degree of amine function substitution with a (C 1 -C 20) alkyl group for the antimicrobial and/or antiviral polymer varies with the polymer and the substituents used, and the degree of substitution is taken as the percentage of the amine-functions in the polymer, and the substitution degree is in the range of from 1 to 100%, and the antimicrobial and/or antiviral polymer is non-covalently adhered to the surface of the product avoiding special modification of the surface.