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West Nile Virus
September 2010

West Nile virus (WNV) is a blood-borne disease that was first reported in the United States in 1999 in New York. Since that time, the virus has spread across the country, and in 2002 the first animal cases were identified in Washington state.

State agencies, including the Washington Department of Fish and Wildlife (WDFW), are working together to minimize public health risks from the disease.

The Washington Department of Health offers more information on WNV human-health issues on its website.

Impacts to fish and wildlife

In various locations around the United States, many species of birds, including songbirds, hawks, owls, eagles, waterfowl, woodpeckers and hummingbirds, have tested positive for West Nile virus.  Corvids (ravens, crows, jays, magpies, etc.) are the group most commonly affected by the virus. Besides birds, some free-ranging mammal species, including caribou, squirrels, wolves, bear and deer, have tested positive for the virus elsewhere in the country. Thousands of wild birds, and many fewer wild mammals, have died from WNV since 1999.

Tips for those recreating outdoors

Because WNV is transmitted by mosquitoes, the best protection from the disease is to avoid mosquito bites. Wear long sleeves, long pants and a hat in mosquito-infested areas and at dawn and dusk when mosquitoes are the most active, and use mosquito repellant when necessary..

Game meat

To protect against wildlife diseases, hunters should follow these standard precautions:

  • Do not harvest or handle wild birds that are obviously sick or found dead.
  • Wear rubber gloves while cleaning game or cleaning bird feeders.
  • Do not eat, drink or smoke while cleaning game.
  • Wash hands with soap and water or alcohol wipes immediately after handling game or cleaning bird feeders.
  • Wash tools and work surfaces used to clean game birds with soap and water, then disinfect with a 10 percent solution of chlorine bleach.
  • Separate raw meat, and anything it touches, from cooked or ready-to-eat foods to avoid contamination.
  • Cook game meat thoroughly, to an internal temperature of 155 to 165 degrees Fahrenheit.

For more information, visit the Centers for Disease Control’s website at

Hunting dogs

Dogs used in wild bird hunting are at minimal risk of contracting WNV and developing illness (see and/or consult your veterinarian).

Mosquito control for property owners

Because mosquitoes lay their eggs in or near water, and larvae require water to survive, property owners can reduce mosquito-breeding areas by:  

  • Emptying anything that holds standing water — old tires, buckets, plastic covers and toys.
  • Making sure roof gutters drain properly and cleaning clogged gutters each spring and fall.
  • Fixing leaky outdoor faucets and sprinklers.
  • Cleaning and changing water in bird baths, fountains, wading pools and animal troughs at least twice a week. Where feasible, pools can be aerated with underwater pumps to keep water moving.

Planting native vegetation and installing nest boxes can help attract mosquito-eating birds and bats. However, property owners should avoid introducing non-native fish or wildlife in an attempt to control mosquitoes. Non-native fish should not be released into open or partially contained waters that may occasionally flood into natural water bodies.

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