A method for obtaining a new antiviral compound with multiple action against many viruses, comprising modified highly purified yeast RNA, a pharmaceutical composition comprising such RNA, and a method for the treatment and prevention of viral disease comprising administering to a patient a composition comprising an amount effective to ameliorate the symptoms of viral disease of ribonucleic acid. The exogenous modified yeast RNA has a pronounced multiple anti-virus action in a wide range of concentrations. The modified yeast RNA is capable of inhibiting the reproduction of viruses from Orthomyxoviridae, Paramyxovirus, Hepatitis, Herpesviridae families, enterovirus and adenovirus. Also, the modified yeast RNA is capable of inhibiting the reproduction of influenza viruses, hepatitis C virus, genital herpes, human immunodeficiency virus and Coxsackie B virus.