2026 West Nile Virus Activity
2026 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 at 2026 West Nile Virus Activity Map.
Mosquito surveillance data available at VectorSurv Maps.
| Exposure Category | Number of Cases |
|---|---|
| In-state, multi-county exposure* | 0 |
| In-state, single county exposure | 3 |
| Out-of-state or unknown exposure location* | 1 |
| Total cases reported among residents | 4 |
* "Multi-county Exposure" represents human cases that had potential exposure in more than one county.
** "Out-of-state or unknown exposure location" represents human cases that had potential exposure in other states or countries exclusively or in addition to Washington State.
Not listed on the table: One resident tested positive for WNV on blood donor screening but did not report symptoms of disease. This person resides and was likely exposed in Benton County.
| County | Human, By County of Likely Exposure | Human, By County of Residence | Horse/Other Mammal | Bird | Mosquito Sample |
|---|---|---|---|---|---|
| Benton | 1 | 1 | 2 | 8 | 52 |
| Franklin | 1 | 1 | 1 | 0 | 2 |
| Grant | 0 | 0 | 0 | 0 | 23 |
| Yakima | 0 | 0 | 0 | 0 | 39 |
| Thurston | 0 | 1 | 0 | 0 | 0 |
| Walla Walla | 1 | 1 | 0 | 0 | 0 |
| Total | See table above | See table above | 3 | 8 | 116 |
Past West Nile Virus Activity
Final annual West Nile virus surveillance maps and statistics for 2002-2025
More Surveillance Data
The Washington Tracking Network presents 2006-2025 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 and Statistics
CDC West Nile Virus Statistics and Maps - West Nile virus surveillance data and maps on human infections and activity by state.