Academic, scientific or professional interest: Virology is a discipline with a wide range of implications. As the COVID-19 pandemic has shown, viral infections play a key role in human health and can strongly condition our lives. However, the current pandemic is only the latest in a series of viral emergencies resulting from the transmission of viruses between animals and humans, including HIV/AIDS, variants of influenza, Ebola and the Zika virus, among others, to which must be added infections caused by other human viruses. In addition, viruses have a major impact on food production, both in agriculture and livestock, being ubiquitous and highly diverse entities with an important role in ecosystems. Finally, viruses and their derivatives have been the source of many innovations in molecular biology and biotechnology, providing practical proteins, expression vectors and even therapeutic agents against tumours or antibiotic-resistant bacteria. Therefore, the scientific, technological and social importance of viruses is unquestionable. This Master's proposal aims to adopt a generalist and integrative approach, including the implications of viruses in human, animal and plant health, but also the biology, evolution and biotechnological applications of viruses.