How dengue expanded around the world

From nine countries to more than 100

Dengue is a viral infection spread by Aedes mosquitoes. According to WHO, only nine countries had experienced severe dengue epidemics before 1970. It is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. Reported cases rose from about half a million in 2000 to 5.2 million in 2019.

2024: the largest year on record

In 2024 WHO received reports of 14.4 million cases and more than 11,000 deaths in all six WHO regions. More than 13 million of those cases were in the Americas. Brazil, Colombia, Peru and Paraguay all had historically large epidemics.

Reported cases are only part of the picture. One modelling study estimated about 390 million dengue infections a year, of which about 96 million cause symptoms.

Mosquitoes on the move

The main vector, Aedes aegypti, spread around the tropics with shipping and thrives in cities, laying eggs in water containers. The Asian tiger mosquito, Aedes albopictus, has spread to every continent except Antarctica in recent decades, partly through the trade in used tyres. It tolerates cooler climates, which is why it matters for Europe.

Why the map keeps growing

Several drivers overlap: fast-growing cities with poor water supply and waste management, more travel that brings the virus to places where mosquitoes are already waiting, and warmer temperatures that lengthen transmission seasons and extend the mosquitoes’ range. One modelling study projected that more than two billion additional people could be at risk by 2080.

Dengue in Europe

Dengue is not endemic in mainland Europe, but local transmission now happens every summer. ECDC records locally acquired outbreaks in France and Croatia from 2010, in Spain from 2018 and in Italy from 2020. There were 130 locally acquired cases in 2023. In 2024, France, Italy and Spain reported 308 local cases.

Dengue on the map

The dengue layer uses OpenDengue, an open collection of national dengue case counts. It starts with a single record from the United States in 1924 and grows from the 1960s onward: 73 countries reported in 1980, 95 in 2000 and 120 in 2024, when Brazil alone reported more than 10 million cases. Where countries published monthly or weekly counts, fine navigation shows dengue month by month. 2025 is still incomplete.

Countries count dengue differently. Some report suspected cases, others only laboratory-confirmed ones, and the definitions change over time. The map keeps the published totals as they are rather than harmonizing them. For diseases whose maps have shrunk, see malaria in Europe and smallpox.

Common questions