West Nile virus (WNV) is an infectious disease that first appeared in the United States in 1999. Infected mosquitoes spread the virus that causes it. People who get WNV usually have no symptoms or mild symptoms. The symptoms include a fever, headache, body aches, skin rash, and swollen lymph glands. They can last a few days to several weeks, and usually go away on their own.
If West Nile virus enters the brain, however, it can be life-threatening. It may cause inflammation of the brain, called encephalitis, or inflammation of the tissue that surrounds the brain and spinal cord, called meningitis. A physical exam, health history and laboratory tests can diagnose it.
Older people and those with weakened immune systems are most at risk. There are no specific vaccines or treatments for human WNV disease. The best way to avoid WNV is to prevent mosquito bites:
- Use insect repellent
- Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets or barrels
- Stay indoors between dusk and dawn, when mosquitoes are most active
- Use screens on windows to keep mosquitoes out
NIH: National Institute of Allergy and Infectious Diseases
Prevention and Risk Factors
Statistics and Research
- NIAID's Role in Addressing West Nile Virus (National Institute of Allergy and Infectious Diseases)
Journal ArticlesReferences and abstracts from MEDLINE/PubMed (National Library of Medicine)
Find an Expert
- FAQ: Pregnancy and Breastfeeding (Centers for Disease Control and Prevention)