This book is intended as a practical and accessible introduction for those who are new to the field of viral infectious diseases and bioinformatics. It is designed for students, early-career researchers, and anyone looking to explore these topics from the ground up. The book covers basic scientific concepts and provides an overview of the epidemiological aspects of viruses, with a focus on simple analytical methods used to study viruses and viral diseases in the context of public health and computational biology. It introduces fundamental informatics tools for virus research, including software tools and databases, while also covering basic theory, algorithms, and applications in viroinformatics and computational virology. Key topics include the virus life cycle, virus evolution, virus-host interactions, and emerging viral diseases.