The branch of enquiry which studies viruses at the molecular scale is called molecular virology. Viruses have a considerable level of biological diversity, and are able to parasitize and infect all kinds of life forms. On the basis of their replication strategy, viruses can be categorized into various classes such as single stranded DNA, double stranded DNA, single stranded RNA-positive sense and single stranded RNA-negative sense. Viruses can cause different types of infections in the hosts. A few such types of infections are acute infection, abortive infection, persistent infection and chronic infection. The study of the replication cycle of viruses is also undertaken within this field. This book contains some path-breaking studies in the field of molecular virology. It attempts to understand the multiple branches that fall under this discipline and how such concepts have clinical applications. Scientists and students actively engaged in this field will find this book full of crucial and unexplored concepts.