Dengue is an infection caused by the dengue virus of which there are four different types (serogroups). The disease is transmitted through the bite of an infected mosquito. The mosquitoes that spread dengue usually breed in urban areas close to human habitation and are most active during daylight hours. Although unpleasant, dengue is usually a self-limiting illness. However a small, but significant, number of people can develop more severe, life-threatening infection.
The disease is common in the tropics. Affected areas include the Caribbean, South and Central America, Africa, Asia and the Pacific Islands. Although less common, outbreaks are increasingly being reported outside tropical areas, including in Europe, with locally acquired cases reported in Croatia, France and Madeira. Dengue does not occur naturally in the United Kingdom (UK), it is a travel-associated infection. Cases of dengue in UK travellers are increasing, with most reported in travellers who visited Asia, the Americas and the Caribbean. Country-specific information on dengue is available on our Country Information pages and current dengue outbreaks are listed on our Outbreak Surveillance database.
All travellers to dengue endemic countries are at risk of dengue infection. The chance of contracting dengue is determined by several factors, including destination, length of exposure and season of travel. Risk is thought to be higher during periods of intense mosquito feeding activity (two to three hours after dawn and during the early evening) Travellers, who spend long periods in areas where dengue is common, are at increased risk, but even short-term visitors can be infected.
Most people infected with dengue remain symptom-free. If symptoms do occur, the illness usually begins abruptly with a high fever, and is often accompanied by a severe headache, muscle and joint pain, nausea, vomiting and a rash. Most infections are self-limiting, with a rapid recovery three to four days after the rash appears.
A small number of people develop more severe illness with symptoms which can include dangerously low blood pressure (shock), fluid build-up in the lungs and severe bleeding. There is no specific drug treatment for severe dengue illness, although hospital admission and careful management of fever, fluid balance and pain can help with recovery. If left untreated, severe dengue illness can be fatal.
Travellers can check our Country Information pages for information on the risk of dengue at their destination. Mosquito bite avoidance is recommended. As dengue is spread by day-biting mosquitoes, particular care with bite avoidance is advised during the day, especially around dawn and dusk. There is currently no vaccine available to prevent dengue in travellers.