The course introduces students to the fundamental concepts of virology and their relevance to human health, ecosystems, and society. It explores the nature and diversity of viruses, virus structure and replication strategies, modes of transmission, and interactions with host organisms. Core principles of immune responses to viral infection, vaccination, and antiviral control. Beyond clinical perspectives, the course emphasizes the role of viruses in public health, environmental systems, and global disease surveillance. It introduces emerging and re-emerging viral diseases, zoonotic spillover, environmental and waterborne viruses, and the One Health framework. No prior virology experience is required.