Question to the Department of Health and Social Care:

To ask the Secretary of State for Health and Social Care, what steps he is taking to increase public health surveillance following the detection of West Nile Virus genetic material in UK mosquitoes.

In May 2025, the Animal and Plant Health Agency (APHA) reported fragments of West Nile virus genetic material in a small sample of mosquitoes collected in Nottinghamshire during July 2023, as part of the RADAR surveillance programme. There is no evidence to suggest ongoing circulation of the virus in animals or mosquitoes, and there have been no locally acquired West Nile virus detections in humans in the United Kingdom. The UK Health Security Agency (UKHSA) has assessed the risk to the general public as very low.

The UKHSA partners with the Department for Environment, Food and Rural Affairs and the APHA on the surveillance of mosquitoes, birds, horses, and humans for a range of emerging infectious diseases, including West Nile virus.

Human health surveillance relevant to the West Nile virus includes routine testing of travellers who have returned from overseas areas affected by West Nile virus with compatible clinical syndromes, including undiagnosed encephalitis.

The NHS Blood and Transplant service screens donors returning from affected areas based on their travel history, and partners with the UKHSA on a research study to understand the risk of climate-related emerging infections, including West Nile virus.

The UKHSA’s clinical testing protocols require that any undiagnosed human cases of encephalitis are referred to the UKHSA’s Rare and Imported Pathogens Laboratory. They will be routinely tested for West Nile virus, regardless of travel history.

Following the detection in mosquitoes, the UKHSA issued a briefing note to National Health Service clinicians nationally on the potential clinical presentation of vector borne diseases, including West Nile virus.

The UKHSA Imported Fever Service offers a clinical advisory and testing service to support doctors managing domestic cases of undiagnosed encephalitis. The British Infection Association’s testing guidelines for encephalitis are being updated to include consideration of the West Nile virus.