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West Nile Virus Activity

The Oregon Health Authority, Public Health Division works with local health departments, mosquito control districts and other agencies to detect and test for the presence of West Nile virus in animals and humans.  Additional information is obtained from health care providers, veterinarians and diagnostic laboratories to improve our surveillance system.

2023 Data

Oregon Cases

County Map


Number Positive

Mosquitoes (pools)
As of October 2023

U.S. West Nile cases by state - CDC website

Data from Previous Years

All files are PDF format.

2020 2019 2018 2017
2016 2015 2014 2013
2012 2011 2010 2009
2008 2007 2006 2005
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All files PDF format

2018​  2017 2016
2015 2014 2013 2012
2011 2010 2009 2008
2007 2006 2005 2004

Suspect Cases

If you find a sick or dead bird

Birds are a natural host for West Nile virus; in Oregon particularly crows, ravens, jays, magpies, and sage grouse. A large or continuous die-off of birds may be a local indicator of WNV activity.

Contact one of the following Oregon agencies for collection and testing for West Nile virus surveillance:

If you suspect a horse has WNV infection

Veterinarians are required to report horses with the appropriate clinical signs. Refer to West Nile Virus testing for further information and contact the Oregon Dept. of Agriculture at 503-986-4760 before submitting horse samples.

Other animals

Any other animal suspected of having West Nile virus or other viruses carried by mosquitoes will be tested at a laboratory. If you have any questions, please call the state public health epidemiologist on call at Oregon Health Authority, Public Health Division, 971-673-1111.