Page last reviewed: 13/07/2011

Dengue is an infectious disease caused by a virus. The virus is transmitted by a type of mosquito (Aedes aegypti) that bites during daylight hours.

The dengue virus belongs to the Flaviviridae family of viruses that cause diseases in humans. Dengue is the most common infection caused by viruses transmitted by mosquitoes (these are known as arboviral illnesses).

Dengue causes severe flu-like symptoms, such as:

  • a high temperature (fever) of 40C (104F) or over
  • severe headache
  • muscle and joint pain
  • facial flushing and skin rash

Who is at risk?

Anyone can catch dengue if the disease is common in that area (endemic). See the box, below left, for a list of high-risk countries.

However, dengue is more common among older children, adolescents and adults. The risk of travellers catching dengue depends on several factors, including:

  • the countries they visit
  • how long they stay in an endemic area (although even short-term visitors may be vulnerable to dengue)
  • the season of travel (mosquitoes breed in fresh-standing water, such as puddles and collected rainwater)
  • the intensity of dengue transmission in that area.


Dengue is a self-limiting disease. Self-limiting means that it clears up by itself, usually within a couple of weeks. The incubation period (the time it takes for symptoms to show after infection) for dengue is five to eight days.

There is no vaccine to prevent you becoming infected, although research into developing a vaccine to protect against dengue is in progress.

The only way to prevent getting the virus is to avoid being bitten and to be particularly careful around the hours of dawn and dusk.

There are no specific medications available to treat the disease, but symptoms can be managed by taking paracetamol, drinking plenty of fluids and resting.

Most people with dengue recover within two weeks. However, in some cases dengue can develop into dengue haemorrhagic fever (DHF). This is a potentially fatal complication of dengue where you bleed from your nose, gums and inside your body. It can also lead to dengue shock syndrome (DSS), a serious complication of dengue haemorrhagic fever that can lead to shock (a sudden loss in blood pressure). This is also potentially fatal.

Dengue is a notifiable disease in Ireland.  Further information on Dengue Fever and Dengue Haemorrhagic Fever is available on the website of the Health Protection Surveillance Centre at

At-risk countries

Dengue virus is most common in:

  • Southeast Asia
  • the Pacific Islands
  • Africa
  • South and Central America
  • the Caribbean
  • Mexico
  • Australia
  • Hawaii
  • the Indian subcontinent

In 2009, large numbers of dengue cases were reported in Brazil. Over 226,000 cases reported within the first 15 weeks of the year. Large numbers were also reported in Bolivia and Argentina.

According to the World Health Organization, each year there are 50-100 million cases of dengue.

Page last reviewed: 13/07/2011

Symptoms of dengue include:

  • feeling as if you have a severe case of flu
  • severe headache
  • eye pain
  • a high temperature (fever) of 40C (104F) or over (this can last for up to five days)
  • severe aching in your joints (dengue is also known as 'breakbone fever')
  • severe muscle pain (myalgia) of the lower back, arms and legs
  • nausea and vomiting
  • chills (shivering)
  • flat red skin rash (it may appear two to five days after the fever starts, and a second rash that looks similar to measles appears when the disease has progressed)
  • facial flushing

These symptoms can be mild in some people and severe in others. All symptoms vary depending on age. Infants and young children usually have a high fever and a rash.

Page last reviewed: 13/07/2011

The dengue virus

Dengue is spread by a type of infected mosquito called the Aedes aegypti mosquito. The mosquito bites during daytime hours, particularly around the hours of dawn and dusk.

There are four different strains of the dengue virus: DEN 1, DEN 2, DEN 3 and DEN 4. They can all potentially cause either classic dengue or a more serious form of the disease called dengue haemorrhagic fever (see Dengue - complications).

Growing populations and an increase in global travel have resulted in the transmission of the virus between different populations.

Transmission of the dengue virus happens in a cycle. An infected human is bitten by a mosquito, the infected mosquito then bites another human, and the cycle continues. Jungle animals in Africa and Southeast Asia can also become bitten and infected with the virus, contributing to the spread of the disease.

Risk factors

Factors that increase your risk of being bitten by a mosquito include:

  • travelling during the rainy season
  • staying in cities of high-risk countries, particularly slums with few or no public health measures

The risk of contracting dengue haemorrhagic fever is increased if you have been infected with a dengue virus before.

Page last reviewed: 13/07/2011

If you think you could have dengue, go straight to your nearest healthcare professional (either a GP or hospital). If you go to a local doctor who is familiar with dengue, they will probably be able to diagnose the condition just by looking at you and asking about your symptoms.

Your medical and travel history will be taken and you will be asked about your exposure to mosquitoes.

You will also be given a blood test to see if the dengue virus is present in your bloodstream. If specific antibodies (proteins produced by your immune system to help fight infection) to the dengue virus are found in your blood, a diagnosis of dengue will be made.

Prompt medical advice from a healthcare professional familiar with the progression and complications of dengue haemorrhagic fever frequently saves lives.

Ruling out other conditions

It is very important to get a diagnosis as soon as possible. The symptoms of dengue can be confused with other conditions such as malaria, which will need to be ruled out before you can be treated.

Page last reviewed: 13/07/2011

As dengue is a virus, there is nothing doctors can do to 'cure' it. All you can do is rest, take painkillers and drink plenty of water.

However, if you have been diagnosed with dengue, it is best to be treated under the supervision of medical professionals in case your symptoms get worse. In hospital, your symptoms will be managed by:

  • monitoring your fluid levels to keep them balanced
  • monitoring your temperature
  • monitoring your blood

A vaccine or specific treatment to help treat dengue or dengue haemorrhagic fever has not yet been developed, because the four different strains of dengue virus make it difficult to develop a vaccine.
If you are somewhere with no medical help:

  • Rest as much as you can.
  • Drink plenty of fluids, but make sure these are clean (buy bottled water and do not drink from the tap).
  • Take rehydration salts to replace lost fluids and minerals.
  • Do not take anything with aspirin or ibuprofen, as they can increase your risk of internal bleeding (take paracetamol instead).

Getting back to normal

You will feel very weak and unwell for a while. Most people recover within two weeks, although it can sometimes take months for you to get back to normal. If you are worried about any aspect of your treatment or diagnosis when abroad, see a doctor when you get home. Tell them where you have been, what your symptoms were and what treatment you received.

Page last reviewed: 13/07/2011

Dengue fever can result in the following complications:

  • dengue haemorrhagic fever
  • dengue shock syndrome

These two conditions are rare in occasional travellers to endemic areas, being more common in people who live in an area affected by Dengue and have been repeatedly exposed to the virus.

Dengue haemorrhagic fever

Dengue haemorrhagic fever is a potentially fatal complication of dengue that can cause an enlarged liver and, in severe cases, can lead to shock (a sudden drop in blood pressure). This is called dengue shock syndrome (see below).
Symptoms of dengue haemorrhagic fever are the same as those for dengue, but there are sometimes also:

  • tiny spots of blood on the skin
  • larger patches of blood under the skin
  • bleeding from your gums and nose
  • a weak pulse and clammy skin
  • sweatiness
  • a tender abdomen (tummy) and body
  • discomfort (malaise)
  • loss of appetite
  • fatigue (tiredness)
  • sore throat and cough

Four different strains of the dengue virus can cause this complication. If you have previously been infected with one strain of dengue and are infected again with a different strain of the virus, this can cause dengue haemorrhagic fever.
Previous immunity (the body's ability to resist infection) to a different strain of dengue virus plays a role in this serious complication.
You are also at an increased risk of getting dengue hemorrhagic fever if you are female and under 12 years of age.
The main feature of treatment for dengue haemorrhagic fever is keeping the patient's fluids at the right level to prevent dehydration.

Dengue shock syndrome (DSS)

This is a complication of dengue haemorrhagic fever in which the symptoms above can be accompanied by symptoms of shock.

Symptoms of shock include:

  • a sudden drop in blood pressure
  • cold, clammy skin
  • a weak rapid pulse
  • dry mouth
  • irregular breathing
  • dilated pupils
  • reduced flow of urine

Mortality rates can be as high as 40% if this serious complication is not treated. If it is treated, the mortality rate is 1-2%.
If you have any symptoms of dengue, dengue haemorrhagic fever or dengue shock syndrome, seek immediate medical help to prevent the disease progressing.

Page last reviewed: 13/07/2011

There is no vaccine to prevent dengue. The best way to prevent getting the disease is to avoid being bitten by an infected mosquito.

Avoiding insect bites 

To avoid being bitten by a mosquito:

  • Stay away from highly infested areas and (if possible) stay indoors during the hours of dawn and dusk (when mosquitoes are more likely to feed).
  • Wear loose-fitting clothing. Mosquitoes are able to bite through tight-fitting clothes.
  • Sleep under a mosquito net to avoid being bitten at night.
  • Use insect repellent to avoid being bitten. Products containing N-diethylmetatoluamide (DEET) are effective but should not be used on babies under two years old.

See the Health A-Z topic on Preventing insect bites for more detailed information on how to avoid being bitten by a mosquito.

Content provided by NHS Choices and adapted for Ireland by the Health A-Z.

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