Antiviral agents are used for the treatment of viral diseases. Antiviral drugs have been successfully developed and used clinically for a limited number of important human viral diseases notably caused by human immunodeficiency virus (HIV), hepatitis C virus (HCV), hepatitis B virus (HBV), herpes, and influenza viruses. Despite the successes of these antiviral drugs, issues with drug resistance and toxicity remain challenging. These challenges are driving research to identify new drug candidates and to investigate novel drug targets to develop new mechanistic drug classes. Antiviral agents are not available against many viruses that cause human disease and economic burdens; in particular, the development of antiviral agents against emerging, re-emerging, and neglected viruses is increasingly becoming a priority. This book includes six review articles that discuss new antiviral strategies. The reviews either discuss advances relating to a specific virus or new therapeutic targets and approaches. The book includes 15 original research articles reporting new antiviral agents against a variety of clinically and economically important viruses and studies into the prevalence or acquisition of drug resistance. Overall, this book is an exciting collection of new research and ideas relating to the development of antiviral agents.