The dengue virus – a flavivirus of which there are four serotypes.
Dengue is transmitted principally by the Aedes aegypti mosquito, which bites during daylight hours. There is no direct person-to-person transmission. Monkeys act as a reservoir host in west Africa and south-east Asia.
Nature of the disease
Dengue occurs in three main clinical forms:
- Dengue fever is an acute febrile illness with sudden onset of fever, followed by development of generalized symptoms and sometimes a macular skin rash. It is known as “breakbone fever” because of severe muscle, joint and bone pains. Pain behind the eyes (retro-orbital pain) may be present. The fever may be biphasic (i.e. two separate episodes or waves of fever). Most patients recover after a few days.
- Dengue haemorrhagic fever has an acute onset of fever followed by other symptoms resulting from thrombocytopenia, increased vascular permeability and haemorrhagic manifestations.
- Dengue shock syndrome supervenes in a small proportion of cases. Severe hypotension develops, requiring urgent medical treatment to correct hypovolaemia. Without appropriate hospital care, 40–50% of cases can be fatal; with timely medical care by experienced physicians and nurses the mortality rate can be decreased to 1% or less.
Dengue is widespread in tropical and subtropical regions of central and South America and south and south-east Asia. It also occurs in Africa and Oceania. (Map). The risk is lower at altitudes above 1000 m.
Risk for travellers
In countries or areas at risk and affected by epidemics.
There are no specific vaccines or antiviral treatments against dengue fever. Use of paracetamol to bring down the fever is indicated. Aspirin and related non-steroidal anti-inflammatory drugs (NSAIs) such as ibuprofen should be avoided.
Travellers should take precautions to avoid mosquito bites both during the day and in the evening in areas where dengue occurs.