Causes of dengue  

Dengue is spread by infected mosquitoes, usually the Aedes aegypti and albopictus varieties.

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.

Aedes aegypti and albopictus mosquitoes

These mosquitoes bite during the day, most often early in the morning, or in the evening before dusk.

These types of mosquitoes are often found in pools of stagnant water near humans  for example, containers near building sites or other discarded human waste. Old car tyres are a particular problem, because water collects inside them, allowing Aedes albopictus mosquitoes to breed.

Rates of dengue are often high in major cities in the developing world that have poor sanitation.

Risk factors

Your risk of catching dengue increases if you spend time living or working in larger towns and cities in the developing world. For example, many aid workers contract dengue at least once in their career.

Areas of the world where the dengue virus is common include:

  • South East Asia
  • the Caribbean
  • the Indian Subcontinent
  • South and Central America
  • Africa
  • the Pacific Islands
  • Australia

Read more about preventing dengue.


There are four different strains of the dengue virus: DEN 1, DEN 2, DEN 3 and DEN 4. 

Once you are infected by one of the strains, you should develop life-long immunity against that strain, but further infections with a different strain are possible.

If you're infected by a different strain, you have a slightly increased chance of developing more serious complications, such as severe dengue (read more about the complications of dengue fever). This increased risk disappears if you are infected with a third or fourth strain.

Growing populations and an increase in global travel have resulted in the virus spreading.

Page last reviewed: 04/09/2014

Next review due: 04/09/2016