Dutch health agency reports four more West Nile virus deaths as cases reach 56

Outbreak trajectory and latest fatalities

Four more patients in the Netherlands have died from West Nile virus infections, bringing the total number of deaths in 2026 to nine. The Dutch National Institute for Public Health and the Environment (RIVM) reported 12 new human cases between 24 September and 1 October 2026, lifting the overall confirmed case count in the country to 56. Health authorities stated that the outbreak, which started in August 2026, has moved past its peak as weekly infection numbers continue to drop.

Since the previous update (24 September 2026), 12 new patients with West Nile virus have been reported to the RIVM. Four of these patients have died. All new patients contracted West Nile virus through the bite of an infected mosquito.

Provincial distribution and animal surveillance

Confirmed human cases are distributed across six Dutch provinces, with the western province of Zuid-Holland recording the highest concentration. Official records show 32 cases in Zuid-Holland, followed by 12 in Utrecht, five in Noord-Holland, four in Noord-Brabant, two in Gelderland, and one in Overijssel. The majority of confirmed human diagnoses occurred after patients were admitted to hospitals with symptoms, though the RIVM estimates that several thousand people in the Netherlands may have contracted the virus without formal detection.

Surveillance programs also identified transmission among animal populations and insect vectors during the final week of September. Testing confirmed West Nile virus infections in 178 birds, 150 horses, and four batches of mosquitoes across the country.

Transmission cycle and clinical symptoms

The West Nile virus is maintained in bird populations and is transmitted to humans and other mammals primarily through the bite of the common house mosquito (Culex pipiens). Most people infected with the pathogen develop no symptoms or experience mild, flu-like illness that can include fever, headaches, body aches, and skin rashes. In less than one percent of cases, the infection develops into severe neuroinvasive disease, including encephalitis, meningitis, or acute flaccid paralysis resembling polio. The disease is fatal in less than one percent of total infections, with severe risks concentrated among patients requiring hospital care.

Prevention and mosquito control guidelines

To reduce the risk of transmission before insect activity declines with autumn weather, the RIVM published guidance on personal protection and vector management. Residents are advised to eliminate standing water around homes by emptying plant saucers, clearing rain tarpaulins, cleaning roof gutters, and tightly closing rain barrels where mosquitoes lay eggs. For garden ponds, authorities recommend maintaining water quality to support natural predators like water beetles, dragonfly larvae, fish, and amphibians, or installing fountains to disrupt surface water.

The total number of reports of people who contracted West Nile virus in the Netherlands now stands at 56. In most people, West Nile virus was diagnosed after they were admitted to hospital with symptoms. In 2026, a total of nine patients with a West Nile virus infection have died.

Health officials also advise wearing long-sleeved clothing and trousers during dusk and nighttime hours when Dutch mosquitoes are most active. Additional recommended measures include installing window screens, sleeping under mosquito nets, and applying insect repellents containing active substances such as DEET, Picaridin, IR3535, or Citriodiol.