West Nile virus

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

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 West Nile virus since 1999.

Tips for those recreating outdoors

Because West Nile virus 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. Use mosquito repellent when necessary.

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.

The Washington Department of Health offers more information on West Nile virus and the impact to human health.