For the first time, researchers have found genetic traces of the West Nile virus (WNV) in mosquitoes in the United Kingdom. This detection is a product of our ongoing national surveillance program tracking the spread of this virus. What we found instead was really incredible—we stumbled upon something amazing while doing routine mosquito surveillance. This unexpected result indicates a possible change in the prevalence of mosquito-borne diseases within the region.
Those specific samples were collected in July 2023 from High Level Entry wetlands on the River Idle at Gamston in Nottinghamshire. They are part of the Aedes vexans species, which is UK native. Despite being locally abundant within river floodplain lakes, we find this species to be uncommon.
West Nile virus has long been endemic in other parts of the world, such as areas in Africa, Asia, and south Europe as well as the Americas. As WNV has now been detected in UK mosquitoes, we must consider how this will affect public health and the environment.
Understanding West Nile Virus
West Nile virus is mainly transmitted by infected mosquitoes to humans via mosquito bite. An estimated 80 percent of people infected with WNV are asymptomatic. Of those that do, symptoms are typically mild flu-like symptoms that most resolve within a few days. In a small fraction of cases—under 1%—the disease can progress to more serious illnesses, like encephalitis.
The UK Health Security Agency (UKHSA) has not confirmed any West Nile virus infections locally in humans or horses in the UK this year. All of this is fantastic news for the health of the public! Meera Chand, the deputy director at UKHSA, has evaluated the risk to the public at large. When I pressed her on this, she admitted that it’s pretty close to zero.
“The risk to the general public is currently assessed as very low.” – Dr Meera Chand
Potential Pathways and Implications
Experts have pointed to migratory birds as being the probable facilitators of the virus’ introduction into the UK. Professor Grant Hughes from the Department of Vector Biology at the Liverpool School of Tropical Medicine stated that “the virus potentially entered the UK via migratory birds.”
For public health officials and researchers, the first detection of WNV in mosquitoes was a watershed moment. James Logan, a professor of medical entomology at the London School of Hygiene & Tropical Medicine, emphasized the significance of this finding.
“The detection of the virus in mosquitoes marks a significant step in that direction.” – James Logan
In recent years, the distribution of West Nile virus has spread more northward and westward over Europe. This trend excites experts’ fears about the increasing prevalence and variety of vector-borne diseases. Climate change is currently influencing mosquito populations and their habitats in multiple ways.
Call for Increased Surveillance
In light of these new findings, experts are calling for increased surveillance in mosquitoes, birds and humans. Professor Matthew Baylis, chair in veterinary epidemiology at the University of Liverpool, urged that ongoing monitoring is critical to understanding and mitigating potential risks.
Additionally, Dr. Arran Folly highlighted the broader implications of this detection: “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.”
As the public, we can go one step further and educate ourselves on reporting unusual mosquito activity through the state’s mosquito surveillance scheme. This effort aims to gather data that puts researchers in control of data. It equips public health officials to better monitor, respond to, and predict the spread of mosquito-borne diseases.
Dr. Jolyon Medlock, head of medical entomology and zoonoses ecology at UKHSA stressed the importance of public engagement. He encouraged everyone to get involved with these critical initiatives.
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