15 October 2025 | First official West Nile virus infection in a horse
In the Dutch province of South Holland, an infection involving the West Nile Virus was officially confirmed in a horse. The infection was confirmed on the basis of a sample taken by the Netherlands Food and Consumer Product Authority (NVWA). The World Organisation for Animal Health (WOAH) has been notified of the infection.
The infection shows that the West Nile virus had been circulating in the Netherlands. Horses cannot directly infect other animals or humans. The virus can only be transmitted by an infected mosquito. Since mosquitoes are less active at this time of year, the risk of new infections is low.
- For more information about the West Nile virus in horses, see: Westnijlvirus | NVWA (in Dutch).
- For current updates about the West Nile virus in animals in the Netherlands, see the NVWA topic page: Westnijlvirus | NVWA (in Dutch).
- For more information about the West Nile virus worldwide, see: West Nile fever | WOAH.
9 October 2025 | Diagnosis of West Nile virus infection in a horse
A horse in the Dutch province of South Holland has tested positive for West Nile virus infection. The horse was tested after showing symptoms that could indicate a West Nile virus infection. The infection has been confirmed by a laboratory, but cannot be officially reported to the World Organisation for Animal Health (WOAH) because it was not possible to take the sample according to the official guidelines.
An infected horse cannot pass the West Nile virus on to humans or other animals. The West Nile virus can only be transmitted by an infected mosquito. Accordingly, the confirmed equine infection is not an immediate cause for concern, especially at the end of the mosquito season in this area. However, the infection does show that the virus had been circulating in the Netherlands.
More information about the West Nile virus in horses: Westnijlvirus | NVWA (in Dutch).
2 October 2025 | West Nile virus found in mosquito
The West Nile virus was found in a mosquito pool in the Dutch province of South Holland. The mosquito that tested positive was a Culex pipiens/torrentium (common house mosquito) captured around 5 September 2025. The mosquito was found in the course of a research project on viruses in mosquitoes in the Netherlands.
No cause for concern, only extra focus
Based on these findings, the risk that the virus will spread to humans is low. The ongoing studies on the West Nile virus do not show any unusual findings among mosquitoes in other areas of the Netherlands. Moreover, the season in which mosquito bites are common is almost over. Therefore, there is no cause for concern.
The National Institute for Public Health and the Environment (RIVM), the Netherlands Food and Consumer Product Authority (NVWA) and the Municipal Health Public Services (GGD) in South Holland are closely monitoring the situation. They are joined in these efforts by various partners, including Erasmus University Medical Center (Erasmus MC), Wageningen Bioveterinary Research (WBVR), animal health organisation Royal GD, the Dutch Wildlife Health Centre (DWHC) and Sanquin.
West Nile virus
The West Nile virus occurs sporadically in the Netherlands. This virus can be found in birds and is transmitted via mosquitoes. These mosquitoes can spread the virus to other birds, and sometimes also to humans and other mammals, such as horses. There have been no reported cases of humans infected with the West Nile virus in the Netherlands since 2020.