Division of Environmental Health

CONTACT INFORMATION: Our Environmental Health Services office at 10777 Main Street in Fairfax is open during regular business hours 8 a.m. - 4:30 p.m., Monday - Friday. Clinic services are not offered at this location.
703-246-2201 TTY 711
10777 Main Street
Fairfax, VA 22030
Pieter A. Sheehan, REHS
Director, Division of Environmental Health

West Nile Virus and Other Diseases Spread by Mosquitoes

Close up of mosquito on human bodyTell mosquitoes to BUZZ OFF this summer! It is important to know how to help control the mosquito population where you live. Not only are they a nuisance, they have the potential to spread disease, like West Nile virus (WNV).

How West Nile Virus Spreads

WNV is most commonly transmitted to humans from the bite of an infected mosquito. Not all mosquitoes can carry WNV and not all mosquitoes are infected. A small number of human cases have been reported through other means of infection: through blood transfusions; organ transplants; exposure in a laboratory setting; or from a mother to her child during pregnancy, delivery or breastfeeding.

WNV is not spread:

  • From person-to-person or from animal-to-person through casual contact. Normal veterinary infection control precautions should be followed when caring for a horse suspected to have this or any viral infection.
  • From handling live or dead infected birds. You should avoid bare-handed contact when handling any dead animal. If you are disposing of a dead bird, use gloves or double plastic bags to place the carcass in a garbage can.
  • Through consuming infected birds or animals. In keeping with overall public health practice, and due to the risk of known food-borne pathogens, always follow procedures for fully cooking meat from either birds or mammals.

Learn about the WNV transmission cycle.

Symptoms, Diagnosis and Treatment of West Nile Virus

Know the Symptoms of WNV

Serious Symptoms in a Few People. About 1 in 150 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent. About 1 of 10 people who develop severe WNV illness that affects the central nervous system die.

Milder Symptoms in Some People. Up to 20 percent of the people who become infected have symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have become sick for several weeks. 

No Symptoms in Most People. Approximately 80 percent of people (about 4 out of 5) who are infected with WNV will not show any symptoms at all. 

See your health care provider if you have concerns about WNV. There is no vaccine or specific antiviral treatment for WNV infection. Medications can be used to reduce fever and relieve symptoms. In severe cases, people may be hospitalized to receive supportive care.

Learn more about WNV symptoms, diagnosis and treatment from the Centers for Disease Control and Prevention (CDC).


There is no vaccine to prevent WNV in humans. The most effective way to avoid WNV and other mosquito-borne diseases is to tip and toss standing water from your yard and protect yourself against mosquito bites.

Take Steps to Control Mosquitoes Inside and Outside Your Home

  • Once a week, empty and scrub, turn over, cover or throw out items that hold water, such as tires, buckets, planters, toys, pools, birdbaths, flowerpots or trash containers.
  • Use screens on windows and doors. Repair holes in screens to keep mosquitoes outside.
  • Use air conditioning when available. 
    • Sleep under a mosquito bed net if air conditioned or screened rooms are not available or if sleeping outdoors.

Use Insect Repellent

  • Use Environmental Protection Agency (EPA)-registered insect repellents with DEET, picaridin, oil of lemon eucalyptus or IR3535, para-menthane-diol (PMD) or 2-undecanone. When used as directed, EPA-registered insect repellents are proven safe and effective, even for pregnant and breastfeeding women.
  • Always follow the product label instructions.
  • Reapply insect repellent as directed.
    • Do not spray repellent on the skin under clothing.
    • If you are also using sunscreen, apply sunscreen first and insect repellent second
  • Do not use insect repellent on babies younger than 2 months old.
    • Do not use products containing oil of lemon eucalyptus on children under 3 years old.
  • Do not apply insect repellent onto a child’s hands, eyes, mouth, and cut or irritated skin.
    • Adults: Spray insect repellent onto your hands and then apply to a child’s face.

We do not know the effectiveness of non-EPA registered insect repellents, including some natural repellents. To protect yourself against diseases spread by mosquitoes, CDC and EPA recommend using an EPA-registered insect repellent. Visit the EPA website to learn more.

  • Wear long-sleeved shirts and long pants.
  • Treat items, such as boots, pants, socks and tents, with permethrin or buy permethrin-treated clothing and gear.
    • Permethrin-treated clothing will protect you after multiple washings. See product information to find out how long the protection will last.
    • If treating items yourself, follow the product instructions.
    • Do not use permethrin products directly on skin.

West Nile Virus Occurrence in Fairfax County

WNV was first detected in humans in Fairfax County in 2002, when there were 13 cases with one fatality. An average of 3 cases are reported to the Health Department per year. More information about WNV and other human illnesses are available in the Health Department’s Communicable Disease report.

Learn more about mosquito monitoring in Fairfax County.

Other Mosquito-Borne Diseases

The following is a list of some of the other mosquito-borne diseases that can be transmitted to humans:


Fairfax Virtual Assistant