West Nile Virus

UK Status

The UK still considers the public risk very low and there are no known locally acquired human cases. Even so, UKHSA and partner agencies are watching closely because West Nile virus was detected in a UK mosquito for the first time in 2025.

The main concern is preparedness: if mosquito, bird, and climate conditions align, the virus could be introduced or circulate locally for short periods.

What Is West Nile Virus?

West Nile virus is a mosquito-borne virus that usually cycles between birds and mosquitoes. People and horses can also be infected.

How It Spreads

Birds are the natural reservoir for West Nile virus. Mosquitoes that feed on birds can maintain the virus in nature, and can sometimes pass it on to mammals, including people and horses. UK guidance highlights Culex modestus as an important vector in Europe, while APHA detected West Nile virus sequences in native Aedes vexans mosquitoes in Nottinghamshire.

Warmer seasons and changing mosquito ranges increase the chance that the virus could move into areas where conditions are suitable.

Symptoms to Know

Many infections cause no symptoms at all. Others can cause fever, headache, muscle aches, tiredness, and sometimes a rash. Serious neurological disease is uncommon but can happen, especially in older adults and people with underlying health conditions.

What It Means for the UK

The recent mosquito finding does not mean West Nile virus is established in the UK, and it does not mean the public is at immediate risk. It does show that the virus can reach UK mosquitoes, which is why ongoing surveillance, bird monitoring, and mosquito control remain important.

If you travel to areas where West Nile virus is circulating, avoid mosquito bites carefully and seek medical advice if you feel unwell after travel.

Prevention

The best way to prevent West Nile virus infection is to avoid mosquito bites, especially in areas where the virus is known to be circulating. Use insect repellent, wear long sleeves and pants, and ensure window screens are intact to keep mosquitoes out of your home.