West Nile virus infections confirmed in nine people in the Netherlands
The West Nile virus has been confirmed in nine people in the Netherlands since the start of the summer, according to the National Institute for Public Health and the Environment (RIVM). The virus is circulating, according to Sanquin Research, and studies on birds and common house mosquitos. One person has died as a result, and at least one person was hospitalized towards the end of August, the office previously stated.
Of the nine individuals who contracted the infection, one was discovered by a blood bank study carried out by Sanquin Research. "In the other people, West Nile virus was diagnosed after they were admitted to the hospital with symptoms," the public health institute said.
"These patients contracted West Nile virus after being bitten by an infected mosquito. The infections occurred in the provinces of Utrecht, Noord-Brabant, Noord-Holland, and Zuid-Holland." At least one infection has been tied to the Amsterdam region in the past week.
A woman from Drenthe may have died from West Nile virus in early August, stated the regional public health office, GGD Drenthe. She contracted the virus during a trip to the southeastern region of Europe, where her symptoms first emerged.
The first-ever West Nile infection in the Netherlands was diagnosed in a person in October 2020, about four weeks after the virus was first observed in the country. There was not a single reported human case of West Nile virus in the Netherlands in 2025.
Only about 1 percent of those infected with the virus develop dangerously severe symptoms of West Nile fever, which can lead to encephalitis or meningitis. Of this small group, the risk of death is anywhere from 4 to 14 percent, but that risk is twice as high for those 70 years of age or older.
Around one in five infected people develop mild flu-like symptoms, according to the RIVM. This usually includes headache, fever, muscle aches, upset stomach and pain, and diarrhea. In rarer instances, it can also lead to a skin rash or swollen lymph nodes.
So far this year, five cases of infected horses were also under investigation by the Netherlands Food and Consumer Product Safety Authority (NVWA). That was up from three cases last year.
Further studies of birds have also found six more infections in 2026, one fewer than all of 2025. The birds that were researched include wild animals, domesticated pets, and some had already died.
A joint effort has since led to the discovery of West Nile virus in two separate groups of mosquitos. "Doctors, veterinarians, virologists, epidemiologists, and ecologists are working closely together to closely monitor the development and spread of West Nile virus and to take appropriate measures," the RIVM stated.
Three mosquito pools were found to be carrying the virus last year.