Dengue is spread by a type of infected mosquito called the Aedes aegypti mosquito. The mosquito bites throughout the day and night.
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 then you should develop life-long immunity against that strain. But it is still possible to be infected again by a different strain.
If you are 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).
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.
Growing populations and an increase in global travel have resulted in the virus spreading between different groups.
The Aedes mosquito prefers to breed near water and is often found in stagnant water in containers around building sites in urban environments. Rates of dengue are often high in major cities in the developing world which have poor levels of sanitation.
Your risk of catching dengue increases if you plan to 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.
