Antiviral Strategies -- Approaches for the Development of Antiviral Compounds: The Case of Hepatitis C Virus -- Antiviral Agents Acting as DNA or RNA Chain Terminators -- Viral Protease Inhibitors -- Anti-Influenza Drugs: The Development of Sialidase Inhibitors -- Other Inhibitors of Viral Enzymes and Functions -- Inhibitors of Viral Entry -- Interferons and Their Use in Persistent Viral Infections -- Nucleic Acids-Based Therapeutics in the Battle Against Pathogenic Viruses -- Antiviral Gene Therapy -- Antiviral Resistance and Impact on Viral Replication Capacity: Evolution of Viruses Under Antiviral Pressure Occurs in Three Phases -- Antiviral Combination Therapy for Treatment of Chronic Hepatitis B, Hepatitis C, and Human Immunodeficiency Virus Infection -- Socio-Economic Impact of Antiviral Intervention. A crucial issue for antiviral therapy is the fact that all antiviral substances rapidly select for resistance; thus, monitoring and overcoming resistance has become a most important clinical paradigm of antiviral therapy. This calls for cautious use of antiviral drugs and implementation of combination therapies. In parallel, efforts in drug discovery have to be continued to develop compounds with novel mode-of-action and activity against resistant strains. This book reviews the current status of antiviral therapy, from the roads to development of new compounds to their clinical use and cost effectiveness. Individual chapters address in more detail all available drug classes and outline new approaches currently under development.