Dengue fever is a viral disease transmitted to humans through the bite of an infected mosquito, usually Aedes aegypti. There are four distinct dengue virus strains.

What type of illness does dengue virus cause?

Dengue fever (also known as Break Bone Fever) usually causes the sudden onset of high fevers, severe frontal headache, and strong joint and muscle pains. Often there seems to be a partial recovery after 1 to 2 days before symptoms return. Many people also suffer nausea, vomiting, and rash. The rash appears 3 to 5 days after onset of fever and can spread from the torso to the arms, legs, and face.

The illness typically starts from 4 to 7 days after a person is bitten by an infected mosquito, but it can sometimes take up to 14 days for symptoms to appear.

Can dengue cause more severe illness?

Dengue infection occasionally causes a more severe and potentially life-threatening illness associated with bleeding (Dengue Haemorrhagic Fever/DHF) and or a sudden loss in blood pressure (Dengue Shock Syndrome/DSS).

The risk of these more severe types of dengue infection are more likely if someone has had a previous dengue infection with a different strain. International travellers from non-endemic areas such as Australia are generally at low risk of DHF or DSS.

How do humans become infected with dengue virus?

The main mosquito vector for dengue, Aedes aegypti, becomes a carrier of the dengue virus through biting an infected person. It can then pass the infection on to other people it bites.

This mosquito is most frequently found in or near homes and prefers to feed on humans during the daytime. It has two peak periods of biting activity: in the morning for several hours after daybreak and in the late afternoon for several hours before dark. The mosquito may feed at any time during the day, however, it prefers to feed indoors, in shady areas, or when it is overcast.

Aedes albopictus, a mosquito common in south-east Asia and Papua New Guinea, can also be an important dengue vector.

Where does dengue virus occur?

Dengue is a rapidly expanding disease and is now endemic in most tropical countries of the South Pacific, Asia, the Caribbean, the Americas, and Africa, including urban areas.

Dengue fever is not an endemic disease in Australia but cases are confirmed every year in travellers returning to Australia after visits to dengue-endemic tropical and subtropical areas. Over the last twenty five years, local outbreaks of dengue fever have occurred in north Queensland as a result of infected travellers being bitten by an Aedes aegypti mosquito which then spreads the infection to others in the local community.

It is therefore important to rapidly identify and protect any person with dengue fever in an area where the Aedes aegypti mosquito occurs to prevent local spread.

How is dengue fever treated?

No specific treatment for dengue fever is available. Patients are encouraged to rest and drink plenty of fluids, while paracetamol may be used to relieve fever and aches. Aspirin and non-steroidal anti-inflammatory medicines (such as naproxen or ibuprofen) should be avoided because of their anticoagulant properties.

Infected persons should be protected from further mosquito exposure by staying indoors and sleeping under a mosquito-proof net during the first few days of illness so that they can avoid contributing to the cycle of dengue infection.

What can people do to prevent becoming infected with dengue virus?

There is no vaccine or preventive drug that provides protection against dengue infection. The best way to avoid dengue virus infection is to prevent mosquito bites, particularly during the day.

While most mosquitoes are more active during dusk and night time, Aedes aegypti mosquitoes are daytime biters so precautions against being bitten should also be taken during the day.

Travellers and residents in dengue-prone areas should take the following precautions to reduce their risk of dengue infection:

apply insect repellent containing a DEET (diethyl toluamide) on exposed skin;
wear long sleeves and pants (ideally treat clothes with permethrin or another repellent);
ensure screens on windows and doors are secure and keep mosquitoes out; and
remove mosquito breeding sites from around the home.

Mosquitoes can breed in almost any standing water around the home. Common mosquito breeding sites include discarded tyres, uncovered barrels, buckets, flower vases or pots, cans, and cisterns.

Further information for health professionals such as clinical symptoms, is available from the Arbovirus and malaria website.
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