Dengue is an endemic viral disease affecting human population in tropical and subtropical regions around the world, predominantly in urban and semi-urban areas. Dengue fever (DF) and its more serious forms, the dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) are becoming important public health problems. The global prevalence of dengue has grown dramatically in recent decades. An estimated 2.5 billion people in more than 100 countries are at risk of acquiring dengue viral infection with more than 50 million new infections being projected annually, between 20,000 and 25,000 deaths, mainly in children. This book aims to review the possible molecular mechanisms that attribute to the variation of Dengue virus (DENV) disease. Additionally, a description of the animal models that have been developed to study DENV pathogenesis and to test potential vaccines and therapeutics are reviewed. This book also reviews the current understanding of DENV pathogenesis and the challenges confronting vaccine and therapeutic developers. Other chapters in this book examine the responses of target cells, including dendritic cells in people infected with DENV, recent developments in the molecular diagnosis for dengue virus, the mathematical models on dengue transmission and control, and a discussion of the ways in which to prevent and control dengue outbreaks.