Abstract: The invention discloses a functionalised chitosan, or a salt thereof, used in the treatment of pathologies of the respiratory tract or hepatic pathologies, preferably caused by viral infections. It was indeed observed that said functionalised chitosan or salt thereof was able to act as galectin-modulator, modulating in particular galectin-3, and therefore determining a marked reduction in the inflammatory and fibrotic cascade generated by these viral infections. The invention moreover discloses a pharmaceutical composition, as well as a biomaterial, comprising this functionalised chitosan, or a salt thereof.