Dengue

What is it?

Dengue, or dengue fever, is a viral illness caused by infection with the dengue virus (DENV).

DENV is a single‑stranded RNA virus that, like yellow fever virus and Japanese encephalitis virus, belongs to the genus Flavivirus. There are four serotypes of DENV. Immunity against one serotype does not provide protection against the other serotypes, meaning a person can experience dengue more than once in their lifetime. Severe disease is more likely with subsequent infections.

What to look for

Dengue has an incubation period of 3 to 14 days. Most people who are infected experience no symptoms or have mild symptoms which resolve in 1 to 2 weeks. Common symptoms include:

• high fever (40°C)
• severe headache
• muscle and joint pains
• rash
• pain behind the eyes
• abdominal pain, nausea and vomiting
• swollen glands.

In rare cases, infection can progress to severe disease (dengue haemorrhagic fever, dengue shock syndrome) and display symptoms of severe abdominal pain, haematemesis (vomit with blood in it), tachypnoea (rapid breathing), bleeding from the gums or nose, fatigue, lethargy, pale and cold skin, or other unexplained bleeding. Severe dengue is a medical emergency.

How is it transmitted?

DENV is primarily transmitted to humans via mosquitoes. Humans who are symptomatic can transmit the virus 2 days prior to symptom onset until 2 days after the fever has resolved. Asymptomatic cases (without symptoms) are also infectious. In rare cases, DENV can be transmitted through mucous membranes, blood transfusions, needle stick injuries and organ transplants. Maternal transmission during pregnancy (from mother to infant) has been reported and is linked to pre‑term birth, low birthweight and post‑partum haemorrhage (severe bleeding).

Epidemiology

Dengue is now endemic in more than 100 countries across tropical and sub‑tropical areas in the Pacific, Asia, Africa and the Americas. There were 14.6 million cases of dengue reported to the World Health Organization (WHO) in 2024.

DENV is not routinely found in Australia although imported cases (where a person is infected overseas) do occur. Mosquitoes capable of carrying dengue can be found in central and northern Queensland, the Northern Territory, northern Western Australia, and the Torres Strait. Local outbreaks of dengue, although rare, have historically occurred in northern Queensland and the Torres Strait.

Prevention

Physical barriers

The mosquitoes capable of carrying dengue are active during the day. Care should be taken to avoid exposure by:

• wearing long, loose fitting clothes when outdoors
• using mosquito repellents containing picaridin or DEET
• limiting outdoor activity if there are lots of mosquitoes
• using fly sprays, mosquito coils and plug‑in repellent devices
• sleeping under mosquito nets treated with insecticides if sleeping indoors where windows, doors and vents are not covered by insect‑proof mesh (flywire screens), or if sleeping outdoors in an untreated tent or in the open.

Vaccination

Dengvaxia is a live‑attenuated recombinant tetravalent vaccine used for the prevention of subsequent dengue infections only. It is given as a 3‑dose course, with 6 months between each dose, and is suitable only where the all following conditions are met:

• Aged 9–45 years
  and
• Previously infected with DENV
  and
• Intending to reside in highly dengue‑endemic regions for extended periods
  and
  
• The potential benefits of vaccination outweigh the risks.

It is only available through the Special Access Scheme (SAS), on a case‑by‑case basis, through specific application to the Therapeutic Goods Administration (TGA).

Contraindications and precautions

Dengvaxia is not safe for people who have never been infected with DENV before. Given approximately 40 to 80% of dengue infections are asymptomatic and there is no blood test sensitive enough to adequately confirm previous immunity, identifying who can safely be vaccinated is challenging.

Dengvaxia has been linked to vaccine-associated enhanced disease (VAED), a rare phenomenon where a person who has been vaccinated experiences a (usually) more severe clinical presentation of an infection than would normally be seen in an unvaccinated person.

It is a live-attenuated vaccine and therefore must not be given during pregnancy or to immunosuppressed individuals.

Resources

• World Health Organization: Dengue
• Australian Centre for Disease Control: Dengue – CDNA National Guidelines for Public Health Units
• ATAGI advice on the use of Dengvaxia for Australians
• Victorian Department of Health: Dengue virus disease
• European Medicines Agency: Dengvaxia
• Australian Centre for Disease Control: Dengue