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West Nile Virus: Data

The first cases of West Nile virus in humans in Wisconsin were reported in 2002.

In 2022, Wisconsin had six confirmed and probable cases of West Nile virus.

From 2018 through 2022, an average of 11 cases of West Nile virus have been reported each year.

West Nile virus is preventable.

You can see this year's statewide data for West Nile virus in the table and the map at the top of the page.

Case numbers are updated routinely during mosquito season.

Summary data for all other years can be found at the bottom of this page.

For information on national data, visit the CDC (Centers for Disease Control and Prevention) Statistics and Epidemiology page for West Nile virus.

2023 Wisconsin West Nile virus case dataUpdated October 23, 2023
TypeNumber of cases
Human confirmed12
Human probable*6
Mosquito pools35
Equine (horse)5
Avian (bird)5
Counties reporting West Nile virus activity14

*Probable cases have presumptive positive laboratory results without confirmatory testing at CDC.
**Deaths and hospitalizations are included among the confirmed and probable cases.

2023 West Nile Virus Activity

Historical West Nile virus data

West Nile virus cases in Wisconsin

Month of illness onset

West Nile virus cases by month

Age group

West Nile Virus cases by age group

Questions about illnesses spread by mosquitoes? Contact us!
Phone: 608-267-9003 | Fax: 608-261-4976

Last revised April 8, 2024