West Nile Virus: Climate Change’s Expanding Threat to Europe
A deadly outbreak of West Nile virus in North Macedonia has cast a stark spotlight on how climate change is reshaping Europe’s disease landscape. At least five people have died and 43 confirmed cases have been recorded in the Balkan nation, according to VRT NWS, with the majority of infections reported in the past three weeks. Health authorities have declared an epidemic emergency in several municipalities of the capital Skopje and surrounding areas, launching large-scale aerial and ground mosquito spraying operations.
A Virus on the Move
The West Nile virus, first identified in Uganda in 1937, has circulated in Europe since the 1950s, introduced by migratory birds from Africa. It is transmitted to humans through mosquito bites, with birds serving as the natural reservoir. Humans and horses are what scientists call “dead-end hosts” — they can become infected but cannot transmit the virus further.
This year, the virus’s reach has expanded dramatically. The European Centre for Disease Prevention and Control (ECDC) reports that 12 European countries have recorded West Nile virus cases in 2026: Albania, Austria, France, Germany, Greece, Italy, Kosovo, the Netherlands, North Macedonia, Romania, Serbia, and Spain. Cases have been reported in 99 regions — an expansion from 67 regions in nine countries during the same period in 2025, according to spotmedia.ro. Italy leads with 311 cases, followed by Greece with 157.
The Climate Change Connection
Scientists say this expansion is no coincidence. A landmark 2024 study by researchers at Brussels’ VUB and ULB universities, published in Nature Communications, formally demonstrated that climate change is responsible for the spatial expansion of West Nile virus in Europe. By comparing factual climate simulations with counterfactual scenarios that removed long-term climate trends, the researchers showed a notable increase in areas ecologically suitable for virus circulation during 1901-2019 — an increase that largely disappeared in the no-climate-change scenario.
“Until now, the formal establishment of the link between the spread of the virus and climate change was lacking, but our results point to a major role of climate change in the advance of the virus in southeastern Europe,” said Diana Erazo, lead author of the study.
Wim Thiery, climate scientist at VUB and co-author of the study, put it bluntly: “This is the face of climate change. Alongside escalating climate extremes, the emergence of tropical diseases in Europe is unfortunately one of the many logical consequences of our addiction to oil, coal and gas.”
Thiery warns that the threat is moving northward. “Currently we mainly see the Mediterranean region and the Balkans emerging as red zones, but it is quite possible that this will advance further north towards our areas in the future,” he said.
Northern Europe on Alert
That warning is already materializing. In the Netherlands, a blood donor tested positive for West Nile virus in August 2026 — the first human case since 2020. The donor lives in the province of Utrecht and had not recently traveled abroad, according to NOS. A horse and a bird have also tested positive in the country, indicating active virus-carrying mosquitoes.
Belgium has seen similar signs. The first confirmed West Nile virus infection in a horse was officially confirmed on August 7, 2026, according to VRT NWS. The animal, which showed severe neurological symptoms, was euthanized. The virus was also detected in birds in Belgium in May and July 2026, and three crows tested positive in 2025.
Leen Delang, virologist at KU Leuven, confirmed that Belgian mosquitoes (Culex pipiens) are capable of transmitting the virus. Her research group demonstrated for the first time that mosquitoes caught in the Leuven area can be infected with the virus and transmit it through their saliva.
How Dangerous Is It?
Most people infected with West Nile virus never know it. About one in four infected individuals develops symptoms after an incubation period of 2 to 14 days: headache, muscle pain, fever, skin rash, and swollen lymph nodes. The majority recover fully, though fatigue can persist for weeks or months.
However, about 1 percent of infected people develop severe conditions such as encephalitis (brain inflammation) or meningitis. The severe form is more common in older people and can be fatal. Between 1999 and 2021, the United States reported more than 55,000 cases, with over half leading to neurological conditions and about 2,500 deaths.
There is no vaccine for humans and no specific treatment — symptoms are managed with painkillers and supportive care. Health Minister of North Macedonia Saso Klekovski has urged residents to take precautions, including emptying swimming pools and reporting dead birds to authorities, as reported by BGNES.
A Growing Public Health Challenge
ECDC experts emphasize the need for a coordinated European response. Celine Gossner, an ECDC expert, calls for monitoring mosquito populations, engaging communities, implementing specific control measures, and assessing environmental impact. The agency warns that the spread of West Nile virus is occurring alongside the expansion of invasive mosquito species across Europe.
The 2024 study also highlighted a dramatic increase in the population at risk. “Our results show a recent and drastic increase in the number of people at risk of exposure,” said Erazo. “This is partly due to an increase in population density, but climate change remains a crucial factor.”
What to Watch For
As Europe’s climate continues to warm, public health experts expect the virus’s range to keep expanding northward. The ECDC estimates that new cases may occur in the current season, with transmission typically peaking in August and early September.
For now, the most effective protection remains prevention: avoiding mosquito bites through protective clothing, repellents, and window screens, and eliminating standing water where mosquitoes breed. As medical entomologist Bart Knols warned: “There is no vaccine, no medicine. We must prepare ourselves.”
The North Macedonia outbreak, which has already claimed five lives, serves as a stark reminder that climate change is not just an environmental issue — it is a public health emergency unfolding in real time across the European continent.