West Nile Virus Data

2024 West Nile Virus Activity

West Nile virus is detected each year in Washington state. The maps linked below and table displayed on this page show current West Nile virus activity. Human cases are listed by county where the infected person was most likely exposed to the virus and by county where the infected person resides. Monitoring for infected mosquitoes is limited to a few counties due to lack of resources. 

Geographic visualization of the table data is available here: 2024 West Nile Virus Activity Map.

Mosquito surveillance data can be viewed here: https://maps.vectorsurv.org.

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2024 West Nile Virus Activity Map

2019 West Nile Virus Activity
Human cases by county of likely exposure
Human cases by county of residence
Infected horses/other mammals, birds, and mosquitoes.
West Nile Virus Detections in Washington, 2024
County   Human  Horse/Other Mammal    Bird    Mosquito Sample  
By County of Likely Exposure  By County of Residence 
Yakima 0 0 0 0 1
Multi-county Exposure* 0        
In-state Acquired 0        
Out-of-state Acquired 0        
Unknown Exposure Location ** 0        
Total 0 0 0 0 1

* "Multi-county Exposure" represents human cases that had potential exposure in more than one county.

** "Unknown Exposure Location" represents human cases that had potential exposure in other states or countries in addition to Washington State. These cases are not shown on Map 1. Human Cases by County of Likely Exposure.

Maps and statistics are updated daily by 3 PM. This table shows cases of West Nile virus reported in the state.

Past West Nile Virus Activity

Final annual West Nile virus surveillance maps and statistics for 2002-2023

Find more surveillance data

The Washington Tracking Network presents 2006-2021 vector mosquito species, Culex pipiens and Cx. tarsalis, test data by county. It also shows bird and mammal test data. View data in a table, chart, and map format and export data for your own use.

See Washington Tracking Network - mosquito samples, birds, and mammals tested for West Nile virus.

National Surveillance Maps & Statistics

CDC West Nile Virus Statistics & Maps

West Nile virus surveillance data and maps on human infections and activity by state.

More Information