Dengue is the most important arthropod-borne viral disease of public health significance. Its geographic distribution includes more than 100 countries worldwide, where more than 2.5 billion people are at risk for dengue infections. Most people will have asymptomatic infections, but the disease manifestations range from an influenza-like disease known as dengue fever to a severe, sometimes fatal disease characterized by hemorrhage and shock, known as dengue hemorrhagic fever/dengue shock syndrome. Dengue fever and dengue hemorrhagic fever/dengue shock syndrome are caused by the dengue viruses (dengue-1, dengue-2, dengue-3, and dengue-4) transmitted from viremic to susceptible humans mainly by the bites of Aedes aegypti. There is no specific management of dengue infections, no vaccine is commercially available, and vector control is the only alternative for stopping the spread of the disease. Knowledge of several aspects of dengue infections, especially of diagnosis and vaccine development, is continuously evolving, but several issues are still unresolved.