Dengue

Last updated: 01 March 2011

What is the Dengue

Dengue is viral infection that is caused by four dengue viruses (DENV-1, DENV-2, DENV-3 and DENV-4). It is spread by two types of mosquito.

What are the symptoms

Most people who are infected with dengue virus have no symptoms.
People with dengue fever begin to develop illness between 3 and 14 days (usually 4-7 days) after being bitten by an infectious mosquito. Symptoms include sudden fever, chills, severe headache with pain behind the eyes, muscle and joint pain and extreme fatigue. There may also be abdominal pain, nausea and vomiting. A faint red rash sometimes develops on the upper body around the third day. The fever typically lasts around 6 days.
Dengue Haemorrhagic Fever (DHF) is a more severe form of dengue that causes internal bleeding several days after onset of normal dengue fever. DHF occurs more commonly when a person is infected a second time with a different type of dengue virus. DHF is sometimes associated with severe shock (Dengue Shock Syndrome) when fluid leaks from the blood into the body's tissues. Infants, young children and the elderly are more susceptible to Dengue Shock Syndrome.

How is it spread?

The dengue virus can be spread by two species of mosquito: the Dengue mosquito (Aedes aegypti) and the Asian Tiger mosquito (Aedes albopictus). These mosquitoes become infected when they feed on somebody who has dengue viruses in the blood during their infection. Once infected, the virus multiplies inside the mosquito and can infect other people when the mosquito feeds again.

Between 3 and 12 days after a person is bitten by a mosquito carrying dengue virus, the virus may be present in their blood. If this person is bitten by another mosquito while the virus is in their blood, the new mosquito can become infected with the virus and pass it on to other people that they bite.

Dengue is occasionally transmitted through blood transfusions, tissue or organ transplants, by needlestick injuries and by mucous membrane contact with blood that is infected with dengue virus.

Who is at risk?

People who travel to dengue affected areas are at risk. Risk areas are those with Aedes aegypti and Aedes albopictus mosquitoes. Currently Aedes aegypti is found in coastal regions of Queensland north of Gladstone while Aedes albopictus is found in the Torres Strait. These mosquitoes live in many tropical countries throughout Asia, the Pacific, parts of sub-Saharan Africa and the Middle East which are considered dengue-affected areas.

In the past, dengue has been found in the Northern Territory, New South Wales and north Queensland but it is currently limited to north Queensland. Outbreaks have occasionally occurred in and around Cairns and Townsville in recent times.

People with dengue fever usually develop long-lasting immunity to that particular type of dengue virus but are still susceptible to infection with other types of dengue virus.

How is it prevented?

Travellers to dengue-affected areas should avoid being bitten by mosquitoes. The dengue mosquito prefers to live and bite people indoors, especially during daylight and in the early evening. The mosquito hides under furniture and tends to bite around the feet and ankles. People may not notice they are being bitten.
The dengue mosquito prefers to rest in dark areas inside and under houses and buildings. The mosquitoes breed in clean water in man-made containers found in and around the home (eg., rainwater tanks, gutters, old tyres and rubbish).

Travellers to dengue affected areas should stay in accommodation with screened windows and doors, wear loose fitting clothing that covers the arms and legs and apply insect repellent containing DEET or Picaridin to exposed skin, especially during daylight hours and in the early evening. Insecticidal surface sprays inside the home can kill the adult mosquitoes.

There is currently no vaccine against dengue.

People with recent dengue fever can't donate blood until 4 weeks after they have recovered.

How is it diagnosed?

Blood tests can show whether there are antibodies to dengue virus. Blood samples are taken while the person is unwell and then again two weeks later to see if there has been a change in the antibody levels. This can indicate that there has been a recent dengue infection.

How is it treated?

Patients with dengue haemorrhagic fever and dengue shock syndrome may require emergency resuscitation and usually need monitoring and treatment in hospital. There are no specific antiviral treatments against the dengue virus.

What is the public health response?

When laboratories confirm dengue fever, they notify their local public health unit. Public health units follow up each case to determine where the person acquired the infection. This information is important to assist identifying if transmission is occurring in areas considered to be low-risk and to prevent transmission.