West Nile Virus (WNV)

Watch Fairfax County Health Department's video to learn how WNV spreads and how to protect yourself.

Below, you’ll find key facts on how WNV spreads, its symptoms, and ways to stay safe.

What is West Nile Virus?

West Nile Virus (WNV) is a disease transmitted by mosquitoes. It was first discovered in the West Nile Region of Africa and became established in the United States in 1999.
WNV is the most common mosquito-borne infection in Virginia and is most active in the mid-summer months when mosquitoes are most numerous.
Some mosquitoes carry WNV and spread it to people when they bite.
Most mosquitoes do not carry WNV, but the ones that do can cause serious illness or even death.
WNV was first detected in Arlington County in 2000 and has affected many residents.

Most symptoms appear three to 15 days after being bitten by an infected mosquito.

No Symptoms (about 80% of people) – Most people infected never feel sick.
Mild Symptoms (about 20% of people) – Some people develop fever, headache, body aches, nausea, and vomiting. Some also get swollen lymph glands or a skin rash. Symptoms can last a few days to several weeks.
Serious Symptoms (fewer than 1% of people) – A small number of cases lead to severe illness, including:
- High fever, headaches, confusion, and muscle weakness
- Stiff neck, tremors, paralysis, or even coma
- Long-term neurological effects
- In rare cases, death

People 55 and older are at greater risk of developing severe illness from WNV.

There is no vaccine for WNV in humans.
There is no cure, but healthcare providers can treat symptoms and help manage recovery.
If you think you or a family member has WNV, see a healthcare provider.