Dutch researchers have found West Nile virus in a meadow bird during a testing programme, the public health institute RIVM said on Wednesday. This is the first time the virus, which is predominantly spread by mosquitoes, has been found in the Netherlands, the RIVM said.

The virus was found in a common whitethroat, a type of migratory warbler, which was not infected when it was tested in the spring, the RIVM says. This means it is likely to have picked up the virus in the Netherlands.

West Nile virus is largely without symptoms but around 20% of people who are infected will develop mild flu-like symptoms. Around 1% become seriously ill and require hospitalisation.

The bird was discovered as part of the One Health pact, a consortium of researchers led by Erasmus University in Rotterdam, who aim to track down exotic viruses in the Netherlands.

The researchers had already found antibodies to the virus in some birds but this is the first active case, the RIVM said.