How Mosquitoes Are Conquering the World: 4 Charts Explained

Earlier this month, the UK Health Security Agency advised people travelling abroad during the summer holidays to take precautions against mosquito-borne diseases.

However, the risk is no longer confined to tropical countries.

Disease-carrying mosquitoes are spreading into regions of Europe, Asia, the Americas and Australia where they were previously absent. Between June 2025 and April 2026, Aedes albopictus — a mosquito capable of transmitting dengue and chikungunya — expanded into new areas of several European countries, including Portugal, France and Greece.

Global malaria cases also continue to rise. An estimated 282 million malaria cases were recorded worldwide in 2024, up from 273 million in 2023. Around 610,000 people are thought to have died from the disease that year (see ‘Malaria remains a deadly disease’).

Chikungunya, a viral infection that causes fever and severe joint pain, has spread to more than 100 countries over the past two decades. Outbreaks have occurred in China, Italy and France during the past two years. In Cuba, an outbreak that began in July last year killed 46 people. Approximately 14.4 million people worldwide are thought to develop chikungunya each year, with most cases reported in South Asia and Latin America¹.

Dengue infections have also reached record levels. More than 14 million cases and 12,000 deaths were reported worldwide (see ‘Dengue is a growing threat in the Americas’).

Mosquito invasions are accelerating worldwide

The spread of disease-carrying mosquitoes into new regions is accelerating, according to an analysis published last October². Researchers examined records dating back to the fifteenth century, when ships transporting enslaved people from Africa to the Americas also carried mosquitoes such as Aedes aegypti, a species that can transmit dengue, chikungunya and other viruses.

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The researchers found that 45 disease-vector mosquito species have invaded new regions at some point, including 12 species that have done so since 2000 (see ‘Mosquitoes are spreading, and quickly’). “That really indicates a very strong increase in terms of new introductions,” says César Capinha, a biogeographer at the University of Lisbon and co-author of the study.

During the past century, used tyres and live plants have become major vehicles for transporting mosquito eggs and larvae. Adult mosquitoes can also travel long distances in cars, trains and aircraft within just a few hours. “We have this major expansion of the global trade networks, so this allowed many species being transported, which is very often the case with mosquitoes,” Capinha says.

How mosquito-borne diseases are spreading

Aedes aegypti is among the mosquito species introduced to the greatest number of regions². It is now found in approximately 150 countries³. Climate change has made some regions more suitable for the mosquito’s development and survival, says Christovam Barcellos, a health geographer at the Oswaldo Cruz Foundation in Rio de Janeiro, Brazil.

Aedes aegypti needs warm temperatures and rainfall to reproduce. In parts of South America, including southern Brazil, Uruguay and regions of Argentina and Paraguay, these conditions once occurred for only a short period each year. The limited season made it difficult for mosquito populations to become established and transmit disease.

That seasonal pattern is changing. “In many countries, you start to see temperatures rise as early as November, and they stay high through March, April or even May. That widens the window for transmission and that’s our main concern,” Barcellos says.

Consequently, dengue outbreaks are being recorded in parts of South America that were previously free of the disease⁴, including southern regions and cities at high altitudes. Barcellos says that heatwaves are also associated with the spread of dengue across the continent.