Prevent the Spread of West Nile Virus

Release date: 06/23/2011
Sponsored by: Health and Human Services Department, Division

Don’t Let Mosquitoes Make a Meal of You!


As the weather warms, mosquitoes are announcing themselves. Our wet spring has created plenty of mosquito habitat. Avoiding mosquito bites and removing containers of standing water and other items that can become habitat for breeding mosquitoes is your best defense against West Nile Virus. The following prevention tips can reduce the risk of exposure to West Nile Virus: 

Prevent mosquitoes from breeding

The best way to reduce the mosquito population is to drain sources of standing water.

  • Remove sources of standing water such as old tires, flower pots, wheelbarrows and other containers. 
  • Change water in bird baths, ponds, wading pools and pet and animal troughs twice a week.
  • Repair leaking faucets and sprinklers.
  • Clean clogged gutters.
  • Cover trash containers so they don't accumulate water. 
  • Properly maintain swimming pools.
  • Check for containers or trash in places that may be hard to see, such as under bushes.
  • Stocking ponds with Gambusia affinis (mosquito larvae-eating fish) is illegal in Washington State because of concerns that the non-native species will become more widespread in local waterways and compete with native species for food. In Oregon, Gambusia can be placed in closed system ponds. Contact your local vector control for information.

Avoid mosquito bites

  • Use mosquito repellent when you are outdoors. Repellents with DEET, Picaridin or oil of lemon eucalyptus are recommended. Use according to directions, especially when applying to children.
  • Install or repair screens on windows and doors so that mosquitoes cannot get indoors.
  • Consider staying indoors at dawn, dusk, and early evening, when mosquitoes are most active.
  • When possible, wear long-sleeved shirts, long pants, shoes and socks, and hats outside.
  • Place mosquito netting over infant carriers when outdoors.

What is WNV?

West Nile Virus is a potentially serious illness that can affect people, horses, birds, and other animals. It is spread to people and animals by mosquitoes that have fed on infected birds. You cannot get the virus from another person or animal. Most people who are infected with WNV will not have any type of illness. About 20 percent of people infected will develop mild symptoms 3 to 14 days after the bite, such as fever, fatigue, headaches, and body aches. People with questions about WNV symptoms should call their health care provider.

An estimated one in 150 people infected will become seriously ill with neurological symptoms (e.g., muscle weakness, numbness, disorientation, convulsions, paralysis), that may be long-term or permanent. While anybody can become infected with WNV, adults 55 years of age and older who spend time outdoors are at increased risk for developing more severe symptoms.  

There are no vaccinations for humans, but vaccinations are available for horses. Horse owners should contact their veterinarians for more information.

West Nile Virus has been present in Washington since 2002 and in Oregon since 2004. Its spread is unpredictable, but many areas of the country have shown a significant increase in cases years after the introduction of the virus.

Detecting West Nile Virus

Dead Corvid birds, such as crows, jays and magpies may indicate the presence of WNV in an area. You can help to monitor for WNV by calling your local county vector control or public health department to report a dead Corvid.

For more information:


Emilio DeBess, Oregon Public Health, 971-673-1111
Philip Bransford, Washington County, 503-846-8685,