The announcement by the UK Health Security Agency (UKHSA) that invasive Aedes aegypti mosquitoes and larvae at have been found in residential properties in east London has prompted concern from experts.

The initial finding was reported through UKHSA’s Mosquito Watch surveillance scheme and is the first time that Aedes aegypti has been identified breeding in the UK. It is the fourth time this species has been detected in the UK in recent years.

It added control measures have been implemented to destroy the larvae and the area will continue to be monitored closely to identify and eradicate any further mosquitoes and larvae.

The UKHSA operates a range of programmes to monitor mosquitoes and other vectors, providing early warning of new or invasive species and supporting rapid public health action where required.

Dr Jolyon Medlock, head of Medical Entomology and Zoonoses Ecology at UKHSA, said: “While Aedes aegypti can transmit diseases such as dengue, chikungunya and Zika virus in countries where these infections are circulating, the risk to the public from this finding is assessed as very low. There is no evidence that these mosquitoes have caused human infections and importantly, to date, there is no evidence of the mosquitoes or larvae being detected in nearby public areas.

“We believe these mosquitoes are accidental importations. Invasive mosquitoes can hitchhike in vehicles, baggage and imported plants, and if they find a suitable climate, can survive. Despite evidence of breeding in this local area and the recent heatwaves, the species is not established in the UK and cannot survive long-term in the typical UK climate, which is too cold overall. However, it is expected that in a warming climate, we will continue to see incursions of invasive mosquitoes, and increased reports of them being able to survive in the UK.”

Experts said the discovery is a concern,

Professor Heather Ferguson, professor of Infectious Disease Ecology, University of Glasgow, and lead of the Mosquito Scotland project, said: “This finding is significant. The Aedes aegypti mosquito is primarily responsible for the transmission of many diseases mosquito-borne diseases, including Dengue, Zika and Chikungunya viruses.  This mosquito is primarily found in the tropics, which is where the greatest public health burden of these diseases fall.

“Climatic conditions in the UK, including where it was found in London, are currently not likely to be suitable for these diseases to spread – however this could change in in coming years with warming temperatures.  To make sure these diseases do not pose a risk to the UK public in the future, it is important that this mosquito species does not establish in the UK.  In addition to their role in spreading diseases under the right environmental conditions, it can also cause a lot of nuisance biting.  This is definitely something we do not want to get a foot hold in the UK.”

She added: “I would encourage members of the public not panic if they get a mosquito bite.  It may be an annoyance, and lead to some short-term irritation just like when you get a mosquito bite on holiday.  However at present, the risk of getting a tropical disease from a mosquito bite in the UK is extremely low.”

Dr David Weetman, reader in Vector Biology, Liverpool of Tropical Medicine, said the discovery needs to  be taken seriously.

“It is definitely important and raises the profile of what may become a more significant risk in the future as the climate continues to warm, though the risk associated with this particular detection seems low,” he added. “Members of the public need to be more aware of the risks in order to stay as safe as possible.”

Weetman explained: “Both Aedes aegypti and Aedes albopictus are aggressive biters which will readily feed on blood from humans (the females only; males only feed on sugar sources). However, they are very distinctive in colouration – with dark brown to black body colour, white patterning and striped legs. None of the other 30 or so native UK mosquitoes resemble them and the most common human man biter is a much larger mosquito called Culiseta – this is approximately more than twice the size of Aedes mosquitoes and has a more drab appearance. Nevertheless if a reaction to a bite persists or a person feels unwell they should seek medical attention.”

Professor Martin Hibberd, professor of Emerging Infectious Disease at the London School of Hygiene & Tropical Medicine (LSHTM), added: “Finding Aedes aegypti breeding in London is a milestone event as the UK’s rising temperatures drive an increasing risk of contracting zika, chikungunya or dengue infections from their blood meal bites.

“While the current mosquitos are unlikely to be infected, and so the risk to people will be low, their presence may indicate a regular summer event in future years. These mosquitos will not survive the cooler weather of Autumn or Winter, but new introductions next year may lead to breeding again.

“In other parts of the world where this happens, small disease outbreaks can occur if an infected human traveller, perhaps as a result of their journey to a country where these diseases are endemic, is bitten at home by one of these local mosquitos, infecting them. A chain of transmission, from mosquito to human to mosquito, can then be established, with potential disease outcomes, during the summer months.

“These mosquitos live in and around human habitations, and are perfectly adapted to city life, all they need is the right climate conditions, which the UK is now more regularly experiencing. Mosquito detection and eradication programs now need to be activated, to ensure that this does not become a bigger risk.”