Infectious Diseases
West Nile Virus (WNV)
2025-09-12 • Updated 2025-09-19
West Nile Virus (WNV)
Overview
West Nile virus (WNV) is a mosquito-borne flavivirus that cycles mainly between birds and mosquitoes. Humans and horses are dead-end hosts. Most infections cause no symptoms; some cause a flu-like illness; a small proportion develop neuroinvasive disease.
How it spreads
- Vectors: Primarily Culex mosquitoes.
- Reservoirs: Wild birds maintain the virus in nature.
- Seasonality: Risk peaks in late summer and autumn.
- Ecology: Warm, wet conditions (and sometimes drought clustering) amplify transmission.
Recognize symptoms
- Most people: No symptoms.
- Mild illness: Fever, headache, body/joint aches, fatigue, rash.
- Severe (neuroinvasive): Severe headache, stiff neck, confusion, seizures, weakness or paralysis.
Seek urgent care for any neurological symptoms or rapidly worsening illness.
Prevention
- Repellents: DEET, picaridin, or oil of lemon eucalyptus.
- Clothing: Long sleeves/pants; socks/shoes at dusk/dawn.
- Home: Install/repair screens; use bed nets where appropriate.
- Environment: Remove standing water (gutters, pots, birdbaths); cover rain barrels.
Treatment
- No specific antiviral.
- Supportive care: Rest, hydration, fever/pain control.
- Severe disease: Hospital-level care for complications.
Related Topics
- #west nile virus
- #mosquito-borne diseases
- #infectious diseases