Scientists have found eggs of the Aedes aegypti mosquito in the UK for the first time – a mosquito that spreads many tropical diseases.
The eggs were recently discovered in a trap at a freight depot near Heathrow airport and confirmed by DNA testing to be Aedes aegypti. The discovery, led by the UK Health Security Agency, also reported further findings of Aedes albopictus, the “Asian tiger” mosquito, at a site in Kent in summer 2024. Both species are invasive and thrive in warm, humid conditions.
These Aedes mosquitoes matter because they can spread viruses such as dengue, chikungunya and Zika. Outbreaks of these diseases, once confined to the tropics, are now appearing in Europe.
In 2024, Italy recorded over 200 locally acquired dengue cases, mainly in the Marche region, while France and Spain also reported domestic dengue transmission. Chikungunya has become another European concern, with France reporting nearly 500 locally transmitted cases in 2025. Zika has not yet taken hold in Europe, but the same mosquito species could carry it if conditions allow.
Two related viruses, West Nile and Usutu, are also spreading further north across Europe. West Nile virus has caused outbreaks in birds, horses and people across Europe, and has now been detected in the UK for the first time.
In summer 2023, scientists found West Nile virus genetic material in wild mosquitoes from samples collected in Nottinghamshire. Usutu, which mainly infects birds, was first detected in London blackbirds in 2020 and has been found in birds or mosquitoes every year since, making it now endemic to the UK.
Both viruses belong to the same family as Japanese encephalitis, and although they primarily circulate in birds and mosquitoes, they can also incidentally infect humans. They also tend to move together. Usutu often establishes first, with West Nile following as temperatures rise.
The UK Health Security Agency notes that West Nile’s range has recently expanded “to more northerly and western areas of Europe”. Together, these findings show how climate change is shifting mosquito-borne diseases northwards.
Laboratory studies have confirmed that native British mosquitoes could transmit these viruses under local UK-climate conditions. Research has shown several species can become infected and even pass the virus on at typical summer temperatures.
For instance, common native Culex mosquitoes from England were found capable of transmitting Usutu in their saliva at just 19°C. In the same study, Culex pipiens and Culiseta annulata were able to transmit the UK Usutu strain, suggesting the virus could spread northwards.
Another experiment found that the salt-marsh mosquito Ochlerotatus (Aedes) detritus can transmit West Nile at 21°C, but not dengue or chikungunya. Combined, these results demonstrate that native UK mosquitoes are able to carry and transmit viruses like West Nile and Usutu if the right climate conditions occur.
More welcoming
The pattern is clear: climate change and global travel are together loading the dice. Warmer summers, milder winters and heavier rainfall are making the UK more welcoming to these insects.
Climate models already predict that Ae albopictus could become established in southern England within the next few decades. At the same time, more people and goods are travelling between the UK and regions where these diseases are endemic, bringing both mosquitoes and infections with them.
The UK Health Security Agency recorded hundreds of imported dengue and chikungunya cases last year. Each one a potential spark if the right mosquitoes are present.
The Animal and Plant Health Agency, a UK government agency, warns that this northward jump of mosquito-borne diseases is “primarily driven by movement of people and global climate change”.
In plain terms, the UK is warming into range for these tropical “vectors” and the viruses they carry. Already, Ae albopictus breeds widely across continental Europe, while local dengue and chikungunya outbreaks are appearing further north each year. West Nile and Usutu are following a similar path.
The UK’s surveillance network, coordinated by the Health Security Agency with universities and local authorities, is already monitoring sites most at risk of mosquito introductions. This coordinated approach is designed to catch incursions early and keep Britain ahead of a rapidly shifting global disease map.
The combination of a changing climate, international travel and the ability of these insects to thrive means both invasive mosquito species and the viruses they carry are edging closer to establishing in the UK.
The continuing surveillance and early detection will be crucial to catch incursions before they spread. As Britain’s summers grow warmer and wetter, the insects and diseases once confined to the tropics are finding a new home – even in today’s not-so-chilly UK.
