Dengue is caused by any of four closely related viruses, or serotypes (dengue 1–4). Dengue viruses are small single-stranded RNA viruses, and belong to the genus Flavivirus, family Flaviviridae. Dengue is transmitted between people by the mosquitoes Aedes aegypti and Aedes albopictus, which are found throughout the world. In the last 50 years, there has been a dramatic increase in the global incidence of dengue virus infections with an estimated 50 million infections occurring annually in at least 100 countries in Asia, the Pacific, the Americas, Africa, and the Caribbean. Dengue virus infections may cause symptomatic infections or asymptomatic seroconversion. Symptomatic dengue infection has a wide range of clinical presentations which includes severe and nonsevere manifestations. While most patients recover following a self-limiting nonsevere clinical course, a small proportion progress to severe disease, mostly characterized by plasma leakage with or without hemorrhage.

Clinical manifestations

After an incubation period of 3 to 7 days, the illness begins abruptly and is followed by three phases – a febrile phase, a critical phase, and a recovery phase.

Febrile phase

The febrile phase is characterized by high temperature (38.5°C) accompanied by headache, vomiting, myalgia, joint pain, and a transient macular rash. High fever may cause neurologic disturbances and febrile seizures in young children. Hemorrhagic manifestations include a positive tourniquet test, easy bruising and bleeding at venipuncture sites, fine petechiae, epistaxis, gingival bleeding, and mild gastrointestinal bleeding (Figure 183.1, Panel A, B, and C). A palpable liver may be noted, especially in young infants and children. The full blood count examination reveals