Wildflowers bloom in the Sierra Nevada
Wildflowers bloom in the Sierra Nevada

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West Nile Virus Fact Sheet

Drawing of mosquito

What is West Nile Virus (WNV)?

West Nile Virus infection is a mosquito-borne virus and is closely related to St. Louis encephalitis (SLE) virus. In 1999, the first confirmed cases in the United States were all recorded in New York City. Since then, confirmed cases of WNV in animals and humans have occurred in all of the lower 48 states including Nevada.

How do people get West Nile Virus?

Mosquitoes feed on infected birds and pass it on to other birds, animals and people. It is not spread by person-to-person contact.

Who is at risk?

Healthy people of any age can become ill with WNV. It can be fatal or permanently disabling although the majority of people who are bitten by a mosquito with West Nile Virus never develop symptoms.

What are the symptoms?

Common symptoms of mild infections are fever, headache, body ache, skin rash and swollen lymph glands. Those with a more severe infection may experience high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, paralysis and death. In humans, the virus has an incubation period of three to ten days.

Is there a treatment or vaccine?

There is no vaccine or treatment for WNV infection. Most people fully recover from the viral infection and those with severe symptoms may have to be hospitalized to receive supportive care.

What is the Health District doing about West Nile Virus?

The Washoe County Health District Vector-Borne Disease Prevention Program already concentrates abatement efforts on mosquito species that can transmit WNV. The staff uses a variety of methods that are safe to humans and animals to control larval and adult mosquitoes. Testing for WNV on various animal species is conducted to quickly identify the virus so that control can be focused to prevent human cases of the disease. The public can call the Health District to request service for control of biting mosquitoes.

How can I protect myself against West Nile Virus?

While there is no recommendation to limit outdoor activity, there are certain precautions you can take if West Nile virus is found in your area:

  • Limit evening outdoor activity when mosquitoes are most active.
  • When you're outdoors, wear a mosquito repellent containing 20-30% DEET for adults and no more than 10% for children.
  • Do not use repellent containing DEET on children under three.
  • Only adults should apply repellent on a child.
  • Spray repellent on your hands and then apply to your face.
  • Only apply repellent to exposed skin and clothing.
  • Do not use repellent under clothing.
  • Wash treated clothes before wearing them again.
  • Do not apply repellent over cuts, wounds, sunburn or irritated skin.
  • Wear long-sleeved shirts and pants when outdoors for long periods of time.
  • Avoid perfumes and colognes when outdoors for extended periods of time.
  • Repair window screens if needed and make sure window and door screens remain closed.

How do I reduce the mosquito population around my home?

  • Change water every few days in bird baths, pet water bowls, and water troughs for large animals.
  • Mosquito fish or gold fish can be put in large water troughs to eliminate breeding mosquitoes.
  • Clean clogged roof gutters on an annual basis. Roof gutters are easily overlooked and can be an ideal breeding ground for mosquitoes.
  • Aerate ornamental pools or stock them with fish. Water gardens are major mosquito producers if allowed to stagnate.
  • Dispose of tin cans, ceramic pots or similar water holding containers on your property.

How can I protect my pets and livestock?

There is no vaccine for dogs and cats. However, horse owners should ensure their horses are vaccinated against West Nile Virus (WNV), Eastern Equine Encephalitis (EEE) and Western Equine Encephalitis (WEE). Consult your veterinarian for more details.

What about dead birds?

The Vector-Borne Disease Prevention Program tested dead birds in 2004 and 2005 for West Nile Virus. Only a low percentage of birds in 2005 were found to have died from West Nile Virus. Trapping and testing adult mosquitoes for virus turns out to be a better indicator of locations where mosquito control needs to be focused to reduce numbers of infected mosquitoes. Therefore the Vector-Borne Disease Prevention Program will no longer pick up dead birds for West Nile Virus surveillance.

If you have a bird that you want tested for West Nile Virus, you may contact the Nevada State Department of Agriculture Animal Diseases Laboratory (ADL) at 688-1182 ext. 231. ADL will continue to test appropriate birds for West Nile Virus.

If you want to dispose of the bird, you may use rubber or latex gloves to pick it up and put it in a plastic bag. Or, if gloves are not available, use a plastic bag turned inside out and pick up the carcass with your protected hand. With your other hand, wrap the bag around the bird, tie off the bag and place it inside a second plastic bag that you can again tie off or zip lock shut. Double bagging prevents cross-contamination and leakage. Place the double bag inside of an outside garbage can or dumpster.

Where can I get more information on West Nile Virus?

The following sources are available:

Who can I contact via telephone?

Please call the Washoe County Health District at 328-2434 between 8 a.m. and 4:30 p.m.