Three people have died from West Nile virus in the Netherlands this year, according to the Dutch public health institute RIVM.
Health officials confirmed two additional deaths on Thursday, September 10, 2026.
The number of infections detected in the country has also doubled from nine to 18 within one week.
Seventeen patients were diagnosed after developing symptoms that required hospital treatment.
Officials detected the remaining infection while Sanquin Research was screening a blood donation.
The patients contracted the virus from infected mosquitoes in Utrecht, Noord-Brabant, Noord-Holland, Zuid-Holland, Overijssel and Gelderland.
Overijssel and Gelderland were added to the list of affected provinces in the latest update.
Researchers have also found three groups of mosquitoes carrying the virus in the Netherlands.
West Nile virus mainly circulates between birds and mosquitoes. Infected mosquitoes can transmit it to people and horses through bites.
About 80 percent of infected people develop no symptoms.
Around 20 percent experience mild symptoms such as fever, headaches, muscle pain, stomach problems, diarrhoea, swollen lymph nodes or a skin rash.
About one percent develop serious conditions such as meningitis or encephalitis.
Older people and those with weakened immune systems face a higher risk of severe illness.
The virus is also spreading among animals.
Authorities received 53 new reports involving infected horses within one week. This increased the total number of affected horses in 2026 to 58.
Tests also found the virus in 23 dead and 10 living wild birds during the same period.
A total of 39 infected birds have now been reported this year. Researchers recorded a high number of cases among crows and related bird species.
There is no West Nile virus vaccine for people.
You can reduce your risk by using mosquito repellent, wearing clothes that cover your arms and legs and removing standing water around your home.
