Background information on dengue fever

What is dengue fever?
Dengue fever is a mosquito-borne infection that causes a severe flu-like illness, and sometimes potentially lethal complications called dengue haemorrhagic fever and dengue shock syndrome. It is caused by the dengue virus, a member of the Flaviviridae family, of which there are four serotypes: Den 1,2,3, and 4.

Where does dengue fever occur?
The WHO has estimated that 2.5 billion people are at risk of acquiring dengue fever and that approximately 50 million infections occur each year. It occurs in tropical and sub-tropical regions of the world affecting approximately 100 countries in Africa, South and Central America, Asia, eastern Mediterranean, and western Pacific. More recently, a locally acquired case occurred in France in August 2010, the first in mainland Europe since 1928. Primarily, urban and semi-urban areas are affected. In Asia and the Americas, the Aedes mosquito likes to breed in household water storage containers and other waste containers where rainwater can collect. In Africa, the mosquito breeds in tree holes or in 'cup like' leaves where rainwater collects. Dengue fever does not occur in the UK but is reported in a number of UK travellers returning from endemic areas. In 2010, 406 cases of dengue fever were reported in England, Wales and Northern Ireland, a high proportion of whom had acquired their infections in India and Thailand. See the epidemiological data page for more information.

What are the symptoms?
Classic dengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death. The clinical features of dengue fever range from non-existent or mild to severe and vary according to the age of the patient. Infants and young children may have a fever with rash. Older children and adults may have either a mild fever or the classical incapacitating disease with abrupt onset and high fever, severe headache, pain behind the eyes, muscle and joint pains, and a rash.

In certain circumstances, the disease may progress to dengue haemorrhagic fever or dengue shock syndrome, both of which can be fatal. These syndromes are rare in UK travellers. There has been evidence to suggest that a subsequent infection with a dengue virus of a different serotype may be the cause of these two syndromes and they are more common in regions where there are frequent dengue outbreaks, with different serotypes of the virus circulating. More information about these complications is available in the NaTHNaC information sheet on dengue fever.

How do you catch dengue fever?
The dengue virus is transmitted by the bite of an infected female Aedes mosquito. Aedes aegypti is most commonly associated with the transmission of dengue fever although other species, such as Aedes albopictus, may also transmit dengue in certain circumstances. When the mosquito feeds on the blood of a person infected with dengue, the virus enters and multiplies within the mosquito. After about 8-10 days, the mosquito can transmit the virus to another human and can do this for the rest of its life. Dengue is not spread directly from person to person.

How long can you have the infection before developing symptoms?
After being bitten by an infected mosquito, it may take typically between five and eight days for the first symptoms (usually fever and headache) to develop, but it can be shorter or longer in some people.

How can you avoid getting dengue fever?
There is no vaccine or drug to prevent dengue fever. The only way to prevent dengue fever is to avoid mosquito bites. The Aedes mosquito bites during the day particularly around dawn and dusk (as opposed to mosquitoes that transmit malaria, which bite at night between dusk and dawn). A good repellent containing N, N-diethylmetatoluamide (DEET) must be used on exposed skin together with light cover-up clothing. If sunscreen is also being used, repellent must be applied after sunscreen. More information about insect bite avoidance is available from the NaTHNaC website. In endemic areas, dengue control programs rely on the elimination of mosquito breeding sites in the community by regular inspections and insecticide spraying of properties (particularly during an outbreak) and the education of local residents to regularly empty standing water and keep outside areas free from waste items in which water may collect.

How is dengue fever treated?
There is no specific antiviral treatment for either classic dengue or dengue haemorrhagic fever.  Supportive nursing care and careful management of symptoms are the standard treatment.

Is dengue fever catching?
If you acquire dengue fever abroad and become ill on your return to the UK, you cannot pass the infection on to anyone else. The Aedes mosquito needed to transmit the dengue virus is not present in the UK because the temperature is not consistently high enough for it to breed. Dengue fever cannot be passed directly from person to person.

Last reviewed: 6 May 2011