What is West Nile Virus? Symptoms and treatment explained
The UK Health Security Agency (UKHSA) has stressed that the risk to the public is 'very low', but said that surveillance and control activities are being 'enhanced' in light of the findings.
While there have been no cases of West Nile Virus acquired in the UK, seven cases linked to travel have been identified since the year 2000.
Experts say they are looking into how viruses move into the country and how they are transmitted to help identify areas that may be at "increased risk of outbreaks.'
🆕 Today, UKHSA and @aphagovuk have confirmed the first detection of West Nile virus in mosquitoes collected in the UK.
There is currently no evidence of wider circulation in birds or mosquitoes, and the risk to the public remains very low.
📰🔗 https://t.co/aS1vjejBqK pic.twitter.com/7YXKxqXrSl — UK Health Security Agency (@UKHSA) May 21, 2025
What is West Nile Virus?
West Nile Virus is the "leading cause of mosquito-borne disease in the continental United States", the CDC says.
However, experts said that the 'geographic range' has expanded in recent years to more northerly and western regions of mainland Europe.
It is usually found in birds, and usually circulates through bird-biting mosquitoes.
In rare cases, mosquitoes can transmit the virus to humans or horses.
What are the main symptoms of West Nile Virus?
The virus is most commonly spread through the bite of an infected mosquito.
Its symptoms are flu-like and include fever, headache, body aches, vomiting, diarrhea, or rash.
What is the main treatment for West Nile Virus?
While there are no vaccines to prevent it or medicines to treat it in people, you can reduce the risk "by taking steps to prevent mosquito bites".
The CDC adds that the best way to prevent West Nile is to protect yourself from mosquito bites.
This can be done by:
Using insect repellent
Wearing long-sleeved shirts and pants
Treating clothing and gear
Taking steps to control mosquitoes indoors and outdoors
West Nile Virus found in UK mosquitoes for the first time
Health officials at the UK Health Security Agency (UKHSA) say they have found signs of the West Nile Virus in mosquitoes in the UK for the first time.
The UKHSA and the Animal and Plant Health Agency (APHA) said 'fragments of West Nile Virus genetic material' were found in some Aedes vexans mosquitoes collected in wetlands on the River Idle at Gamston, near Retford in Nottinghamshire, in July 2023.
While the UKHSA said the risk to the public is 'very low', it said that surveillance and control activities are being 'enhanced' in light of the findings.
Experts said mosquito-borne diseases are expanding to new areas due to climate change.
The UKHSA said that as temperatures warm due to climate change, tick and mosquito species not currently native to the UK will begin to find the UK's climate more 'bearable'.
Other types of mosquito can arrive in the UK by various means including becoming trapped in cars and lorries crossing borders and in shipping containers.
The UKHSA said there is 'no evidence to suggest ongoing circulation of the virus in birds or mosquitoes in the UK'.
But it said that 'disease surveillance and control activities are being enhanced in light of the findings'.
West Nile Virus has been detected in UK mosquitoes for the first time (Image: Getty Images) And it is issuing advice to health workers so that patients with encephalitis – or swelling of the brain – of an unknown cause can be tested as a precaution.
Dr Meera Chand, from the UKHSA, said: 'While this is the first detection of West Nile Virus in mosquitoes in the UK so far, it is not unexpected as the virus is already widespread in Europe.
'The risk to the general public is currently assessed as very low.
'Vector research of this kind is designed to give us early warning of potential threats so that we can enhance our disease surveillance and control activities and ensure patients receive appropriate testing.'
Professor James Logan, from the London School of Hygiene and Tropical Medicine, said: 'The detection of West Nile virus in even a small number of local mosquitoes is a signal that the door is now open.
"Whether the virus takes hold will depend on a combination of environmental, biological and human factors – including how well we prepare.'
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Dr Arran Folly, from the APHA, added: 'The detection of West Nile virus in the UK is part of a wider changing landscape where, in the wake of climate change, mosquito-borne diseases are expanding to new areas.
'Our primary focus is to understand how viruses move into the country and how they are transmitted.
'Combined, this can help us identify areas that may be at increased risk of outbreaks.'
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