West Nile Virus Data

2021 West Nile Virus Activity

Map 1. Human cases by county of likely exposure Map 2. Human cases by county of residence Map 3. Infected horses/other mammals, birds, and mosquitoes

The map and table indicate where West Nile virus activity is occurring in Washington state. Human cases are shown by county where the infected person was most likely exposed to the virus and by county where the infected person lives.

Ongoing West Nile virus monitoring for infected dead birds and mosquitoes is limited to a few counties due to lack of resources. West Nile virus activity may not be indicated in your county, however, it's likely to be widespread in our state.

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2021 West Nile Virus Activity Map

2019 West Nile Virus Activity

West Nile Virus-Positive Cases in Washington, 2021

County

Human

Horse /
Other

Mammal

Bird Mosquito
Sample

By County of
Likely Exposure

By County of
Residence

Benton 1 1 2 0 13
Franklin 0 1 0 0 4
Grant 0 0 0 0 7
Kittitas 0 0 2 0 0
Klickitat 0 0 1 0 0
Walla Walla 0 1 0 0 11
Whatcom 0 0 1 0 0
Yakima 1 1 5 0 16
Multi-county Exposure* 1        
In-state Acquired 3        
Out-of-state Acquired 1        
Totals 4   11 0 51

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

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

Not listed in the table: Four presumptive viremic blood donors were identified. One is a Walla Walla resident and was likely exposed in their county of residence. The second donor is a Franklin resident and had potential exposure in more than one county. The third donor is a resident of Benton County and was likely exposed in their county of residence. The fourth donor is a resident of Whatcom County and was likely exposed in Arizona.


Past West Nile Virus Activity

Final annual West Nile virus suveillance maps and statistics for 2002-2020

Find more surveillance data

The Washington Tracking Network presents 2006-2020 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