Diagnostics plays a vital role in identifying infectious diseases that have the potential to become an epidemic, such as dengue. Good diagnostics enables identifying the cause of an outbreak and assessing interventions for a better impact. The dengue virus is a member of the family of flaviviruses that cross-reacts serologically with all members of its family. The presenting symptoms do not allow definitive diagnosis because they can be of malaria, dengue, Zika, chikungunya, or one of a host of other possibilities. In children, efficient and accurate dengue diagnostics is very important for the early confirmation of dengue because of its quick progress to severe dengue. Dengue diagnostic assays are wide-ranging—from being a reliable one that is time-consuming and expensive to rapid test kits that substantially vary in their accuracy. Therefore, it is important to know which test is to be used at what time, considering whether the population is in an endemic area, as well as how and when to use these tests, be it for the virus or for its genome, antigens, or antibodies. An ideal diagnostic test is one that can pick the virus early enough, is rapid and easy to perform, and affordable by all communities but such a test is yet not available. This book deals with most of the methods that have been used or developed for diagnosing dengue. It addresses the timeline for the evolution of the virus in the body, the body’s response from the onset of fever, and the role of diagnostics as time progresses. It covers most methods, detailing selected protocols, as well as compares them and assesses the time point at which they are useful. The book will be helpful in determining the right test, at the right time, for the right population.