A method of antibacterial and antiviral surface treatment of flexible cover sheet materials includes: providing a flexible cover sheet substrate; depositing at least one lower support layer on the upper surface of the substrate; providing an antibacterial and antiviral formulation comprising a liquid active sanitizing composition dispersed in a solvent containing a polymer-based solution; depositing the formulation on at least one lower support layer to form an upper antibacterial and antiviral active layer; heating the cover substrate to cause evaporation of the solvent of an upper active layer. The active sanitizing composition contains silver chloride and solid-state titanium dioxide of nanometric size and is intended, to inhibit proliferation of bacterial and viral pathogens on the surface of the substrate, while keeping the properties of the materials thereof unaltered.