Dengue Cases Surge to Record 14.6 Million in 2024 as Climate Change Drives Mosquito-Borne Diseases into New Regions
核心洞察
Global dengue (搜索) cases reached a record 14.6 million in 2024, up dramatically from 505,430 cases in 2000, with the Americas now accounting for 90% of cases.
Climate change, international travel, and global trade are accelerating the spread of Aedes mosquitoes into previously unaffected regions including Europe, with new habitats emerging in cities like London, Zagreb, and Vienna.
There is no specific antiviral treatment for dengue (搜索); management is entirely supportive with fluid management and paracetamol, while the Qdenga vaccine is available in the UK only for previously infected travelers.
Global dengue (搜索) cases have surged to an unprecedented 14.6 million in 2024, according to the World Health Organization, marking a dramatic escalation from just over half a million cases recorded in 2000. The surge has been accompanied by the geographic expansion of disease-carrying mosquitoes into previously unaffected regions across Europe, Asia, the Americas, and Australia, driven by climate change, international travel, and cross-border trade networks.
The Americas now bear the heaviest burden, accounting for 90% of global dengue (搜索) cases. Brazil alone reported over 10 million cases and 6,321 deaths in 2024. Meanwhile, 308 cases were reported to WHO from three European countries — France, Italy, and Spain — consistent with trends from previous years.
A rapidly expanding threat
The rate at which disease-carrying mosquitoes are invading new regions is accelerating, according to an analysis published in October 2024. Researchers reviewing records dating back to the fifteenth century found that 45 disease-vector mosquito species had invaded new regions at some stage, with 12 doing so since 2000. "That really indicates a very strong increase in terms of new introductions," said César Capinha, a biogeographer at the University of Lisbon and a co-author of the study.
Over the past century, used tyres and live plants have become important carriers for eggs and larvae. Live mosquitoes can also travel on cars, trains, and planes, covering long distances in just 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 said.
Aedes aegypti (搜索) leads the list of the most widely introduced mosquito species and is now present in approximately 150 countries. Between June 2025 and April 2026, Aedes albopictus — a mosquito that can transmit dengue (搜索) and chikungunya — spread to new areas in several European countries, including Portugal, France, and Greece.
Climate change widens the transmission window
Rising temperatures are expanding the seasonal window during which mosquitoes can reproduce and transmit disease. Christovam Barcellos, a health geographer at the Oswaldo Cruz Foundation in Rio de Janeiro, Brazil, explained that in parts of South America — such as southern Brazil, Uruguay, and regions of Argentina and Paraguay — warm temperatures and rain used to occur for only a short period each year, insufficient for mosquitoes to become established. "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 said.
A 2025 publication described how climate change has made cities such as London, Zagreb, and Vienna potentially suitable to host dengue (搜索)-associated mosquitoes. The virus is not currently endemic in the UK, but travel-associated cases occur every year — 344 cases were reported in 2025, down from an all-time high of 904 in 2024. India, Thailand, and Indonesia are the most frequently reported travel destinations linked to imported cases.
Clinical presentation and challenges in diagnosis
Dengue (搜索) is a viral infection transmitted primarily through bites from Aedes aegypti (搜索) or Aedes albopictus mosquitoes. The incubation period in symptomatic cases is around four to ten days after infection, with symptoms typically lasting two to seven days. Key symptoms include high fever of 40°C with abrupt onset, severe headache, pain behind the eyes, and muscle and joint pains.
The clinical picture poses diagnostic challenges because the same mosquitoes can also transmit Zika and chikungunya, and the presentation of fever with headaches and malaise overlaps with other travel-associated infections including malaria. Dr Michael Head, senior research fellow in global health at the University of Southampton, noted that most people with dengue (搜索) infection are either completely asymptomatic or present with mild self-limiting symptoms that resolve after one to two weeks. After the main infection clears, patients can experience longer-term fatigue that usually resolves after a few weeks.
Patients who experience second or multiple infections are at greater risk of developing severe dengue (搜索) — previously called dengue haemorrhagic fever. Symptoms include abdominal pain, persistent vomiting, and bleeding gums or nose. Dengue shock syndrome, a life-threatening complication, is characterized by profound hypotension and internal bleeding, which can result in organ damage including kidney and liver failure and death.
The global fatality rate is less than 1%, though rates can reach 10–15% if the condition is left untreated, particularly in severe presentations. Mortality rates tend to be higher in low-income settings where health services are often under-resourced. Most severe dengue (搜索) cases and most deaths occur in children aged under 15 years.
No specific antiviral treatment available
There is currently no specific antiviral or host-directed treatment that cures dengue (搜索) infection. Management is entirely supportive, with fluid management as a key intervention. Paracetamol is the recommended pain relief; ibuprofen or aspirin-containing drugs are not recommended because dengue can cause internal bleeding.
Two dengue (搜索) vaccines are licensed globally — Qdenga and Dengvaxia — but only Qdenga is currently approved for use in the UK. Qdenga is a live, attenuated tetravalent vaccine licensed for individuals aged four years and older, administered as a two-dose schedule taken three months apart. While Dengvaxia is strictly limited to those with previous dengue infection, Qdenga is licensed for both seropositive and seronegative individuals. However, the UK Joint Committee on Vaccination and Immunisation only recommends Qdenga for travelers who have had a prior dengue infection, due to a small risk of severe dengue developing in seronegative individuals if vaccinated and later infected.
Implications for clinical practice
For healthcare professionals, a high fever of 40°C with abrupt onset in a returning traveler is a key indicator of potential dengue (搜索) infection. Clinicians should take a thorough travel history and inquire about possible mosquito bites. Unlike Anopheles mosquitoes that transmit malaria and bite in the evening and at night, Aedes mosquitoes are most active during daylight hours — an important distinction for pre-travel counseling.
Preventive measures recommended for travelers include use of insect repellents, mosquito nets, and protective clothing. If dengue (搜索) is suspected, clinicians should discuss the case with local microbiology, virology, or infectious diseases services. In the UK, the Imported Fever Service provides 24-hour telephone support, and blood samples should be sent to the Rare and Imported Pathogens Laboratory, part of the UK Health Security Agency (搜索).
The African continent is also experiencing a surge in dengue (搜索) cases, described as a "looming threat." The presence of Aedes aegypti (搜索) has been reported in almost all African countries, though the true burden is likely greatly underestimated — patients presenting with fever are often presumed to have malaria, and healthcare worker training and diagnostic facilities for dengue are frequently lacking.
Beyond dengue (搜索), the broader mosquito-borne disease landscape remains dire. Malaria cases worldwide reached an estimated 282 million in 2024, up from 273 million in 2023, with approximately 610,000 deaths. Chikungunya has emerged in more than 100 countries over the past two decades, causing outbreaks in China, Italy, and France, with about 14.4 million people worldwide thought to develop the disease each year.