This book discusses various components of the innate and adaptive immune response in combating viral infections, presenting the recent advances in our understanding of innate immunity recognition of viruses and highlighting the important role of inflammation, cytokines such as interferon, toll-like receptors and leukocytes in the initial detection of invading viruses and subsequent activation of adaptive immunity. It also summarizes the role of the adaptive immunity against viral infections through clearance of virus and establishment of memory response that protects against the recurrent infections. In addition, the book examines the role of DNA and RNA sensors in viral recognition and in controlling viral infection. Lastly, it