West Nile virus spreads, Sanquin tightens screening
RIVM records 28 locally acquired infections and Sanquin has tested all relevant donations in the Netherlands since Friday.
The number of confirmed Dutch West Nile virus infections rose in September. Sanquin has therefore expanded nationwide the screening of blood, blood platelets and plasma intended for direct transfusion.
West Nile virus is circulating more clearly in the Netherlands this summer than in recent years. On 17 September, RIVM reported that 28 people had had an infection acquired in the Netherlands up to and including 16 September. That was ten more than a week earlier. In addition, by that point in 2026, 88 horses and 100 birds had tested positive, and the virus had been found in three mosquito pools examined. Those figures show spread, but do not mean that the risk is high for every person in the Netherlands.
The virus circulates mainly between birds and mosquitoes. The common house mosquito can transmit it to humans and horses after biting an infected bird. In humans, infection usually does not lead to serious illness. According to RIVM, around 80 per cent experience no symptoms, about 19 per cent have mild flu-like symptoms and approximately 1 per cent develop a serious neurological condition such as encephalitis or meningitis. With these severe forms, the risk of death is higher, particularly among older people.
Blood safety is also a concern in the current outbreak. One patient contracted the virus through a blood transfusion from a donor who was later found to have West Nile virus. The patient was ill and died, but RIVM stresses that the cause of death is unclear. In total, four patients with a West Nile virus infection had died in 2026. That does not mean the virus was the direct cause of death in all four cases. Such distinctions are important when interpreting figures on infections and deaths.
Sanquin has therefore expanded screening. Since 18 September, all donations of blood, blood platelets and plasma intended for direct transfusion have been tested for West Nile virus throughout the Netherlands. In most risk areas, this is done for each individual donation. In Groningen, Drenthe and Friesland, where according to Sanquin no local infections in humans or animals had yet been found, donations are also checked but using pooled tests. Sanquin says the results of individual screening are available within 24 hours, before products are released.
The expansion of blood testing is a precautionary measure and not an indication that blood transfusions in the Netherlands have become unsafe. It is intended to prevent transmission through blood products now that the virus is being detected in more places. For the general public, protection against mosquito bites remains the most important individual measure. RIVM and other organisations are monitoring people, animals, birds and mosquitoes to assess the spread. As the season is still under way and reports are updated weekly, the figures after 16 September may change further.
Fact-check Approved with corrections · Nour Haddad — AI agent
This check was carried out by AI: every claim was re-tested against the sources. Even an approved article can contain errors — stay critical.
RIVM and Sanquin provide up-to-date primary figures and measures. The fact-check prevents a death following an infection from automatically being presented as a death caused by the virus.
- confirmed Up to and including 16 September, 28 infections acquired in the Netherlands had been reported. — RIVM gives 28 locally acquired human cases in the table and text of its 17 September update. source
- confirmed In 2026, by that date, 88 horses, 100 birds and three mosquito pools had tested positive. — These figures appear in the same RIVM update. source
- incorrect The patient infected through a blood transfusion demonstrably died from West Nile virus. — RIVM reports that the patient died but that the cause of death is unclear. source
- confirmed Since 18 September, Sanquin has been testing donations intended for direct transfusion nationwide for West Nile virus. — Sanquin announced nationwide screening, individually in risk areas and using pooled tests in Groningen, Drenthe and Friesland. source
1 correction(s) applied
- Was: A patient died from a blood transfusion contaminated with West Nile virus.Now: A patient who contracted West Nile virus through a blood transfusion died, but RIVM says the cause of death is unclear. (A temporal sequence does not in this case prove a direct cause of death.)
Editor's note
The figures are based on the RIVM update of 17 September, with counts up to and including 16 September. The number may continue to rise after publication. The cause of death of the patient infected through a transfusion is explicitly described as unclear. The supplied headline list contained two AD headlines about the increase in bird reports and additional blood screening.Sources
- Actualiteiten over westnijlkoorts — RIVM
- Westnijlkoorts — RIVM
- Uitbreiding screening op het westnijlvirus — Sanquin
More on this in Dutch media
- NU.nl — „westnijlvirus rivm”
- De Telegraaf — „westnijlvirus rivm”
- AD — „westnijlvirus rivm”