July 25, 2024


West Nile virus is a disease spread by infected mosquitoes that mostly affects birds. It can also be transmitted to other animals and people.

You can help prevent the spread of West Nile Virus by reducing the number of mosquitoes around your home and protecting yourself from mosquito bites.

How to reduce mosquitoes and prevent bites»

Report Dead Birds

Some birds, especially corvids such as crows and jays, are known to get sick and die from West Nile virus. Wild bird die-offs can indicate the presence of West Nile virus in our community. 

Multnomah County Vector Control checks dead birds for West Nile seasonally between May 15 and September 30.

You can hep by reporting dead birds online or by calling us at 503-988-3464. If they meet the criteria, we will come out and pick up the carcasses so they can be checked for West Nile.

To report a dead bird outside of these dates:

  • Wildlife Care Center | 503-292-0304
  • Oregon Department of Fish and Wildlife, Sauvie Island Wildlife Area | 503-621-3488

mosquito about to suck human bloodAbout West Nile Virus

In most cases, the virus is spread by the bite of an infected mosquito. Mosquitoes become infected with the virus when they bite an infected bird. They can then spread it to other animals or people.

You can get West Nile virus from:

  • The bite of an infected mosquito
  • Blood transfusions or organ donations from an infected donor (but not from donating blood)
  • Pregnant mothers to unborn children
  • Breast milk (but mothers are still encouraged to breastfeed their babies).

You can’t get it by handling live or dead infected birds. If you handle dead animals it’s still important to wear gloves. Wash your hands thoroughly with hot soapy water after you’ve removed them.

The infection rate of West Nile virus in dogs and cats is a very low. It can causes illness and death in horses, but a vaccine for horses is available. If you are concerned, contact your veterinarian.

Illness and symptoms

It takes 3 to 14 days for a mosquito bite to cause illness. Most people do not become very sick. They may have no symptoms at all, or have a mild illness with fever and body aches. 

Less than one percent of people who get the virus become severely ill with encephalitis. The elderly are at greatest risk for serious illness.

Seek medical care if you were bitten and have these symptoms:

  • Fever
  • Headache
  • Nausea
  • Body aches
  • Other symptoms


West Nile Virus FAQs – English (42.72 KB)
West Nile Virus FAQs – Chinese (424.1 KB)
West Nile Virus FAQs – Korean (247.23 KB)
West Nile Virus FAQs – Russian (189.91 KB)

DEET Brochure (for seniors) (151.62 KB)
Proper insect repellent use for children (31.82 KB)
“Fight the Bite” poster (multiple languages) (3.16 MB)

More Information

Centers for Disease Control & Prevention:

Contact Us

Multnomah County Vector Control
5235 N Columbia Blvd
Portland, Oregon


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