title: "West Nile Virus in Europe: The Silent Threat" date: "2026-04-03" excerpt: "West Nile virus is Europe's deadliest mosquito-borne disease with no vaccine available. Italy reported 455 cases in 2024. Learn the risks and how to stay safe." category: "diseases" author: "Mosticare Editorial"

West Nile Virus in Europe: The Silent Threat

By Mosticare Editorial | Published 2026-04-03

While dengue and chikungunya grab headlines for their explosive outbreaks, West Nile virus (WNV) has quietly become the most lethal mosquito-borne disease on the European continent. In 2024, 19 countries across Europe reported 1,436 locally acquired human cases, with Italy alone accounting for 455 infections. There is no vaccine for humans. There is no specific antiviral treatment. And for the approximately 10 percent of neuroinvasive cases, the consequences can be devastating or fatal.

This is the disease every European should understand but too few have heard of.

What Is West Nile Virus?

West Nile virus is a flavivirus belonging to the same family as dengue, Zika, and yellow fever. First isolated in the West Nile district of Uganda in 1937, it was detected in Europe as early as the 1960s. The virus is maintained in nature through a cycle between birds (the primary reservoir hosts) and mosquitoes (the vectors), with humans and horses serving as "dead-end hosts" -- they become infected but do not produce sufficient viraemia to continue the transmission cycle.

According to the WHO, WNV is now found across Africa, Europe, the Middle East, North America, and West Asia. In Europe, it has transitioned from an occasional imported infection to an annually recurring seasonal disease.

Europe's WNV Landscape: 2024 in Numbers

The 2024 WNV season was one of the most intense on record, trailing only the exceptional years of 2018 (1,549 cases) and 2022 (1,116 cases). The ECDC's historical surveillance data reveals the geographic breadth of the problem:

Country-by-Country Breakdown (2024)

| Country | Locally Acquired Cases | |---------|----------------------| | Italy | 455 | | Greece | 217 | | Spain | 138 | | Hungary | 111 | | Albania | 106 | | Romania | 99 | | Serbia | 63 | | France | 39 | | Austria | 34 | | Germany | 27 | | Croatia | 20 | | Bulgaria | 16 | | Other countries | 111 |

The transmission season ran from March through October, with the earliest case reported on 1 March and the latest on 25 October 2024.

Italy: Europe's WNV Epicentre

Italy has consistently reported the highest WNV case counts in Europe. The Po Valley -- with its flat terrain, extensive irrigation systems, rice paddies, and wetlands -- provides ideal breeding habitat for Culex pipiens, the primary European vector. The Emilia-Romagna, Veneto, and Lombardia regions are perennial hotspots. Italian authorities have responded with mandatory blood supply screening during transmission season and extensive mosquito surveillance programmes.

Greece, Romania, and Hungary: The Balkans-Danube Corridor

The Danube River basin and its associated wetlands create a corridor of WNV activity stretching from Romania through Hungary and into the Balkans. Greece, which experienced a devastating outbreak in 2010 (262 cases, 35 deaths), has maintained heightened surveillance ever since. In 2024, Greece reported 217 cases, confirming the disease's persistent presence in the eastern Mediterranean.

The Vector: Culex pipiens

Unlike dengue and chikungunya, which are spread by Aedes mosquitoes, WNV in Europe is primarily transmitted by Culex pipiens, the common house mosquito. This distinction has profound implications for risk assessment:

Ubiquitous distribution: Culex pipiens is found across virtually all of Europe, from Portugal to Finland. Unlike Aedes albopictus, which is limited to 16 countries, Culex mosquitoes are already everywhere.
Dusk and dawn biting: Culex mosquitoes are most active during twilight hours and at night, meaning risk extends into the evening.
Breeding in polluted water: Culex mosquitoes breed in stagnant water, including drains, septic tanks, and polluted pools, making them harder to eliminate than Aedes species.
Bird-mosquito cycle: The virus circulates between birds and mosquitoes, with periodic spillover into human and equine populations during periods of high mosquito abundance.

Symptoms: The 80/20/1 Rule

WNV infection follows a distinctive pattern that explains why it is called "the silent threat," as described by the WHO and the CDC:

Approximately 80 Percent: No Symptoms

The vast majority of WNV infections are entirely asymptomatic. Infected individuals never know they were bitten by an infectious mosquito. While this may seem reassuring, it means the true burden of infection is vastly underestimated -- the 1,436 reported European cases in 2024 likely represent only the tip of the iceberg.

Approximately 20 Percent: West Nile Fever

Around one in five infected people develop West Nile fever, a flu-like illness characterised by:

Fever
Headache
Fatigue and body aches
Nausea and vomiting
Occasional skin rash
Swollen lymph nodes

Symptoms typically appear 2 to 14 days after the mosquito bite and resolve within a few days to several weeks. However, fatigue can persist for months.

Fewer Than 1 Percent: Neuroinvasive Disease

In fewer than 1 percent of infections, WNV crosses the blood-brain barrier and causes neuroinvasive disease. This is where the danger lies. Neuroinvasive WNV can manifest as:

Meningitis: Inflammation of the membranes surrounding the brain and spinal cord, causing severe headache, stiff neck, and sensitivity to light.
Encephalitis: Inflammation of the brain itself, potentially causing confusion, seizures, tremors, paralysis, and coma.
Acute flaccid myelitis: A polio-like syndrome causing sudden limb weakness and paralysis.

The mortality rate for neuroinvasive WNV is approximately 10 percent overall, rising to 20 percent for patients aged 70 and above. Survivors of encephalitis frequently experience long-term neurological sequelae, including cognitive impairment, weakness, and depression.

No Vaccine, No Specific Treatment

This is the most critical point: unlike many other infectious diseases, there is no licensed vaccine for WNV in humans. While effective vaccines exist for horses, human vaccine development has stalled in clinical trials for decades due to the relatively small (from a global perspective) number of cases and the challenges of conducting efficacy trials for a disease with unpredictable seasonal outbreaks.

Treatment for WNV is entirely supportive. Mild cases require rest and fluids. Neuroinvasive disease often requires hospitalisation, intravenous fluids, respiratory support, and management of complications. There are no approved antiviral drugs for WNV.

This means that prevention is the only tool available.

Risk Factors: Who Should Be Most Concerned?

Age

The single greatest risk factor for severe WNV disease is age. According to a 2024 JAMA Network Open study, people over 60 are disproportionately affected by neuroinvasive disease, with mortality rates approaching 20 percent in those over 70.

Immunosuppression

Organ transplant recipients, cancer patients undergoing chemotherapy, and individuals on immunosuppressive medications face mortality rates of 30 to 40 percent if they develop neuroinvasive WNV, as documented in StatPearls clinical reference data.

Geographic Location

Residents of the Po Valley in Italy, the Danube basin, the Greek lowlands, and the Spanish interior face the highest risk. However, the expanding range of WNV in Europe means that previously unaffected areas -- including parts of France, Austria, and Germany -- are increasingly seeing cases.

Outdoor Activities at Dusk

Because Culex mosquitoes are most active at twilight and night, people who spend time outdoors in the evening -- dining al fresco, gardening, exercising -- are at heightened risk during transmission season (June to November).

Prevention: Practical Steps for Europeans

For Homeowners and Families

Eliminate breeding sites: Culex mosquitoes breed in stagnant water. Clear blocked gutters, empty paddling pools when not in use, maintain swimming pool chlorination, and address any areas of standing water on your property.
Install physical barriers: Window screens, door screens, and mosquito nets are highly effective against Culex mosquitoes, which often enter homes to bite during the night.
Use outdoor protection during evenings: If dining or socialising outdoors after dusk in affected areas, employ mosquito-repelling measures and wear long sleeves.
Protect sleeping areas: Since Culex mosquitoes bite at night, ensuring bedrooms are mosquito-free is essential. Bed nets, screened windows, and fan circulation all reduce bite risk.

For Businesses and Hospitality

Hotels, restaurants, and outdoor venues in WNV-affected areas should implement mosquito management programmes, including professional monitoring, barrier treatments in outdoor dining areas, and guest advisories during transmission season.

For Public Health Authorities

Blood supply screening remains a critical intervention. Italy and several other affected countries now mandate WNV nucleic acid testing (NAT) of blood donations during transmission season, a measure that has prevented transfusion-transmitted infections.

Climate Change and the Future of WNV in Europe

The northward and westward expansion of WNV in Europe is closely linked to climate change. As outlined by the European Climate and Health Observatory, warmer temperatures accelerate mosquito development, extend the transmission season, and increase the rate of viral replication within mosquitoes.

The appearance of locally acquired cases in Austria (34 cases in 2024), Germany (27 cases), and France (39 cases) -- countries where WNV was essentially unknown a decade ago -- demonstrates that the threat is moving north. Climate projections suggest that by 2030, much of central Europe could fall within the WNV transmission zone.

Frequently Asked Questions

Can you get West Nile virus in northern Europe?

Cases have been reported as far north as Germany and Austria. While the highest risk remains in southern and southeastern Europe, the geographic range is expanding annually.

How is West Nile virus different from dengue?

WNV is transmitted by Culex (common house) mosquitoes, primarily at night. Dengue is transmitted by Aedes mosquitoes during the day. WNV has a higher neuroinvasive risk but lower overall symptomatic rate. There is no human WNV vaccine; dengue vaccines exist but have limited European availability.

Should I be tested for West Nile virus?

If you develop fever, headache, or neurological symptoms during mosquito season (June-November) in an affected area, consult your doctor. Diagnosis is confirmed through blood tests detecting WNV antibodies.

About Mosticare: Mosticare develops chemical-free mosquito protection solutions for homes, businesses, and communities across Europe. Our mission: a green, mosquito-free life for every European. Learn more

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