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West Nile Virus: Data

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

In 2021, Wisconsin had eight confirmed and probable cases of West Nile virus.

From 2017 through 2021, an average of 20 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 to the right and in the map below. 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 Centers for Disease Control and Prevention (CDC) Statistics and Epidemiology page for West Nile virus.

2022 Wisconsin WNV Case Data

Updated November 30, 2022

Human confirmed 5
Human probable* 0
Deaths** 0
Hospitalizations 5
Equine (horse) 2
Avian (bird) 1
Counties reporting WNV activity 7

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


West Nile Virus Activity

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 March 6, 2023