Dengue fever is a mosquito-transmitted viral infection. It is common in most tropical and subtropical countries.

Approximately 390 million dengue virus infections occur each year, of which 500 000 require hospitalisation.

The Aedes aegypti mosquito is the primary host of dengue.

The virus is transmitted to humans through the bites of infected female mosquitoes of the species Aedes aegypti. This vector can also transmit other infections (chikungunya, yellow fever and Zika infection).

The virus has an incubation period of 4–10 days.

An infected mosquito can transmit the virus for the rest of its life.

Severe dengue (also known as dengue haemorrhagic fever) was first recognised in the 1950s during dengue epidemics in the Philippines and Thailand.

Today, severe dengue is one of the leading causes of hospitalisation and death among children and adults in these regions.

There are four distinct, closely related, serotypes of the virus that cause dengue (DEN-1, DEN-2, DEN-3 and DEN-4). Recovery from infection by one provides lifelong immunity against that particular serotype. Cross-immunity to the other serotypes after recovery is only partial and temporary.

Further infections by other serotypes increase the risk of developing severe dengue.