West Nile virus detected in Britain's mosquitoes for first time

Telegraph

21-05-2025

The West Nile virus has been detected in mosquitoes in the UK for the first time, health officials have announced.
Fragments of the virus, which belongs a group that can cause dengue and yellow fever, were identified in Aedes vexans mosquitos found in wetlands on the River Idle near Retford, Nottinghamshire.
There have been no confirmed human cases of the virus in Britain and the current risk to the public is 'very low', the UK Health Security Agency (UKHSA) said.
But it added that 'disease surveillance and control activities are being enhanced in light of the findings'.
The warming climate has meant different species of mosquitoes, and the viruses they carry, are increasingly able to survive on the British Isles, raising the prospect of other deadly diseases such as malaria becoming commonplace in the future.
The virus is already commonly found across Africa, Asia and the Americas, and has expanded in recent years to more northerly and western parts of Europe.
Since 2000, seven cases have been identified in Britain from those who have contracted the virus abroad.
Infects the brain and nervous system
Most people will experience no or minimal flu-like symptoms, according to the Government's guidance, but around one in 150 cases can be severe.
As well as a fever, headache, and fatigue, other symptoms can include rashes on the limbs, neck or trunk, as well as swollen lymph nodes.
In severe cases, it can infect the brain and nervous system, presenting as meningitis, encephalitis (brain swelling), or a very sudden onset of weakness 'with high fever, neck stiffness, disorientation or confusion, severe muscle weakness, tremors, convulsions, paralysis and coma'.
New advice has been issued to doctors and healthcare professionals to test for the virus in cases where a cause of brain swelling or inflammation could not be found.
Those aged over 50 years old or with underlying conditions such as cancer, high blood pressure or diabetes, were at greatest risk, while fatality rates were highest in the over 70s.
Early-warning system
Dr Meera Chand, the deputy director for travel health and emerging infections at UKHSA, said the finding was 'not unexpected as the virus is already widespread in Europe'.
She added that 'research of this kind is designed to give us early warning of potential threats so that we can enhance our disease surveillance'.
The West Nile virus is usually found in birds and circulates through bird-biting mosquitoes but can be transmitted to horses as well as humans.
Dr Arran Folly, an arbovirologist at the Animal and Plant Health Agency and the lead of the Vector-Borne RADAR project, tasked with identifying new threats, said it was '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,' he said.