Dengue fever, also known as breakbone fever, is an infectious tropical disease caused by the dengue virus and transmitted by mosquitoes. Dengue fever virus (DENV) is a virus of the family Flaviviridae, genus Flavivirus and contains a single-stranded RNA genome with positive polarity. There are four serotypes of the virus, which are referred to as DENV-1, DENV-2, DENV-3 and DENV-4. The geographical distribution is around the equator, particularly Latin America, Central Africa, India, Southeast Asia, Western Pacific and South of the USA. Dengue viruses are transmitted to humans through the bites of infective female yellow fever mosquitoes (Stegomyia aegypti, formerly Aedes aegypti). The mosquitoes generally acquire the virus while feeding on the blood of an infected person. After virus incubation for eight to ten days, an infected mosquito is capable, during probing and blood feeding, of transmitting the virus for the rest of its life.

Yellow fever mosquitoes are well adapted to living in close proximity to humans, and to feeding off people rather than other vertebrates. They prefer to lay their eggs in artificial water containers, such as flower vases, uncovered barrels, buckets and discarded tires. The incubation period ranges from 3-14 days, but most often it is 4-7 days. Typically, people infected with dengue virus are asymptomatic or only have symptoms of a common cold. The characteristic symptoms of dengue are sudden-onset fever (up to 40 °C) with intense headache (especially behind the eyes), and muscle and joint pain. In combination with a skin rash these symptoms are known as the ‘dengue triad’. This usually lasts 3-7 days. In some patients the disease proceeds to a critical phase. Dengue Hemorrhagic Fever (DHF) or Dengue Shock Syndrome (DSS) occur in less than 5 % of all cases of dengue. About 1-5 % of severe cases are fatal. In individual epidemics the case-fatality rate may reach up to 15 %. Infection with one serotype is believed to produce lifelong immunity to that serotype but only short-term protection against the others. Secondary infection with a different serotype may result in severe clinical manifestations. There is no vaccination available.