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The number of people who have died from West Nile virus in the Netherlands this year has risen to three, and the number of known infections has doubled in the space of a week, the national public health institute RIVM has reported. It is a marked escalation of a virus that, until recently, had barely been seen in people in the country.
The latest figures
In its weekly update, published on Thursday, the RIVM said nine new patients had been reported since the previous week, bringing the total number of infections caught in the Netherlands this year to 18, up from nine. Three people have now died, compared with one reported a week earlier. Out of respect for the privacy of the people involved and their families, the RIVM is not giving further details about them.
The virus is also spreading geographically. A week ago, people had been infected in four provinces; now it is six: Utrecht, Noord-Brabant, Noord-Holland, Zuid-Holland, Overijssel and Gelderland. Most of the new patients were admitted to hospital with symptoms, while one infection was again picked up through screening of blood donors by Sanquin Research.
There are signs of the virus circulating more widely in animals too. The food and product safety authority (NVWA) has now recorded 58 horses with West Nile virus this year, and a working group tracking the virus reported dozens more infected wild birds, both living and dead, in the past week alone.
What the virus is
West Nile virus circulates mainly in birds and is spread to people, horses and other mammals through the bite of the common house mosquito (Culex pipiens). It does not spread from person to person, the only exceptions are the rare cases of transmission through a blood transfusion or organ donation, which is why blood banks screen for it.
For most people, the infection is mild or unnoticeable. According to the RIVM, around 80 percent of those infected have no symptoms at all, and about 19 percent develop mild, flu-like illness. In roughly 1 percent of cases, the virus causes inflammation of the brain or the membranes around it. For that small group, the risk of dying is estimated at between 4 and 14 percent, rising to between 15 and 29 percent in people over 70. There is no vaccine and no specific medicine; treatment is limited to supporting the patient.
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Why the Netherlands is concerned
If most infections are harmless, why is the Netherlands so concerned?
Firstly, this is a recently introduced virus to enter the Netherlands. West Nile fever was recorded in someone who caught it in the country for the first time only in October 2020. From 2022 to 2025 there were no human infections at all. Until in 2025, the first infected horses appeared, and now, in 2026, there is a small number of human cases, three of them fatal. A virus that was essentially absent is now, within a single season, killing people, and doubling its case count week on week.
Secondly, the research implies that the virus appears to be establishing itself locally. The infections are being confirmed not just in people but across the whole chain the virus needs to go through to continue to exist: in wild birds, in horses, and in the common Dutch house mosquito itself. That combination suggests West Nile is not a one-off case tourists bring from southern Europe. It is now circulating within the Dutch environment, growing and spreading.
Thirdly, the changing climate. West Nile virus has been moving north across Europe in recent years, and warmer summers create better conditions for the mosquitoes that carry it. The virus’s arrival and apparent establishment in the Netherlands fits a pattern that scientists link to a warming climate, with the possibility that it might be here to stay.
How to protect yourself
Since there is no vaccine for people, avoiding mosquito bites is the main precaution. Mosquitoes are most active around dusk. The RIVM advises wearing covering clothing such as long sleeves and trousers, using mosquito repellent on exposed skin, fitting insect screens on windows and doors, and, where appropriate, sleeping under a mosquito net.