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 the statewide data for West Nile virus in the table.

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

Case numbers are updated routinely during mosquito season.

2022 Wisconsin WNV Case Data

Updated September 23, 2022

Human confirmed 1
Human probable* 0
Deaths** 0
Hospitalizations 1
Equine (horse) 2
Avian (bird) 1
Counties reporting WNV activity 4

* 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 (2002-2021)

West Nile virus cases in Wisconsin

Cases reported by month and age


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: September 23, 2022