With the exception of influenza viruses, all the other highly pathogenic viruses considered in this book lack a specific licensed antiviral drug treatment. Despite the efforts to identify new targets and strategies, we are still unprepared in counteracting both existing and future viral pathogens that threaten worldwide public health due to their pandemic potential and great pathogenicity, which is associated with high mortality rates. The current SARS-CoV-2 pandemic has taught us how unprepared we are when a novel pathogen is introduced in the human population and how it is important to invest and to focus scientific efforts on the development of new, effective, specific drugs and therapeutic strategies against current and future emerging viral pathogens.