Disease-carrying mosquitoes have expanded into new regions across Europe, the Americas, Asia, and Australia, threatening billions with mosquito-borne diseases.
The geographic range of disease-vector mosquitoes is accelerating into new territories worldwide, bringing pathogens such as dengue, chikungunya, and malaria to regions that previously remained unaffected, according to an analysis published in October. Researchers reviewing historical records dating back to the fifteenth century found that 45 disease-vector mosquito species have invaded new regions, with 12 of those introductions occurring since 2000. César Capinha, a biogeographer at the University of Lisbon and a co-author of the study, noted that the data signals a strong increase in new introductions.
Global Trade Networks and the Rapid Spread of Aedes Species
Modern global logistics have transformed how mosquito species travel across continents. Over the past century, used tyres and live plants have emerged as primary carriers for eggs and larvae. Live mosquitoes also hitch rides on cars, trains, and planes, allowing them to traverse long distances within hours. Capinha explained that the major expansion of global trade networks permits many species to be transported easily.
Among the most widely introduced species is Aedes aegypti
, which transmits both dengue and chikungunya viruses and is now established in roughly 150 countries. Between June 2025 and April 2026, a related vector species, Aedes albopictus
, expanded into new territories across multiple European nations, including Portugal, France, and Greece. The UK Health Security Agency issued warnings earlier in the summer holiday season advising travellers abroad to protect themselves against mosquito-borne infections.
Climate Change Widens the Transmission Window in South America
In South America, climate change is altering environmental suitability for mosquito development. Christovam Barcellos, a health geographer at the Oswaldo Cruz Foundation in Rio de Janeiro, pointed out that rising temperatures allow Aedes aegypti
to thrive in areas where conditions were previously unfavourable.
Historically, regions in the south of Brazil, Uruguay, and parts of Argentina and Paraguay experienced warm and rainy conditions for only brief periods each year, limiting the mosquito’s ability to establish and transmit diseases. That pattern has shifted. According to Barcellos, temperatures now begin rising as early as November and remain elevated through March, April, or May. That widens the window for transmission and that’s our main concern,
Barcellos said. Consequently, dengue outbreaks are appearing in places that were previously free of the disease, including southern regions of the continent and cities at high altitudes, with heatwaves further driving the progression.
Global Case Counts and Record-Breaking Disease Outbreaks
The territorial expansion of mosquitoes coincides with surging global case numbers for major vector-borne illnesses. Malaria cases worldwide climbed to an estimated 282 million in 2024, compared with 273 million in 2023, with an estimated 610,000 fatalities, according to World Health Organization figures.
Chikungunya has similarly emerged in more than 100 countries over the past two decades, triggering outbreaks in China, Italy, and France over a two-year span. An outbreak in Cuba beginning in July of last year resulted in 46 deaths. Globally, approximately 14.4 million people contract chikungunya annually, predominantly across South Asia and Latin America.
Dengue has reached record levels globally. Pan American Health Organization data indicates that reported dengue cases surpassed 14 million, accompanied by 12,000 deaths worldwide.
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