Dengue is a viral fever and is caused by 4 types of closely related viruses.

Dengue viruses spread to humans by the bite of female mosquitoes. These mosquitoes acquire the virus while feeding on the blood of an infected person. The virus circulates in the blood of infected humans for 2 –7 days leading to fever. Recovery from infection provided immunity against that particular virus but offers only partial protection against the other three viruses. Infact, subsequent infection increases the risk of a more complicated fever called as "dengue hemorrhagic fever".

In infants and young children, dengue presents as a mild fever with rash. Older children and adults may have the classical symptoms of high fever, severe headache, pain behind the eyes, pain in the joints and muscles and rash. The pain in the back may be so severe that it is also called as backbreaking fever. Dengue fever is usually self-limiting.

Dengue hemorrhagic fever is characterized by high fever, bleeding and liver enlargement. It requires urgent hospitalization as it may even lead to death.

Treatment for dengue and dengue hemorrhagic fever is supportive. Painkillers may be needed for severe bodyache. The patient should take adequate fluids to prevent dehydration. In case of bleeding or any other complications, patient may require hospitalization.

The only method of preventing dengue is controlling the mosquito infestation. The mosquito causing dengue primarily breeds in man-made containers like metal drums, earthenware jars and other water storage jar. Proper solid waste disposal and improved water storage practices, including covering containers should be encouraged. Insecticides should used periodically. For travelers, going to affected areas, use of mosquito repellents is advised.

Vaccination is not yet available. Vaccine development is difficult because any of the four different viruses may cause disease and because protection against only one or two dengue viruses could actually increases the risk of dengue hemorrhagic fever.