MADISON, Wis. (WMTV) – Wisconsin health officials are investigating a case of measles confirmed in a person who traveled through Milwaukee Mitchell International Airport to Walworth County.

Wisconsin Department of Health Services (DHS) officials said this case is linked to a confirmed case in another state. It comes as the DHS Wisconsin Monitoring Program found measles in untreated wastewater in Walworth County.

This is the first time measles had been found in wastewater in Wisconsin, health officials noted.

“This is a new public health surveillance method that was developed in advance quite a bit during the COVID pandemic. And scientists and public health laboratories around the country, around the world, realized that if we test for viruses, for the genetic material of viruses in wastewater, it can sometimes give us an early warning sign,” explained Dr. Ryan Westergaard, Chief Medical Officer, DHS Bureau of Communicable Diseases.

Dr. Westergaard says since July, they have been testing 44 sewer sheds, and this was the first positive measles detection.

The detection coincides with a case that was reported by someone currently isolating in Walworth County.

DHS stated this case was exposed to measles out of state and is not linked to cases in Dane County.

The person who tested positive for measles flew through Mitchell International Airport on January 29th, according to the City of Milwaukee Health Commissioner. He says the person was infectious during the flight.

Anyone who was at the Mitchell International Airport between 10:30 p.m. and 12:31 a.m. may have been exposed.

“We’ve been working with our partners at the state and with other health officers in the state of Wisconsin and the CDC to ensure that notification goes to the individuals that we are aware of that we’re on the plane,” explained Mike Totoraitis, City of Milwaukee Health Commissioner.

He says the individual flew on a Southwest Airlines flight WN266 from Phoenix to Milwaukee.

Totoraitis says people should check their vaccination status and monitor symptoms.

“Make surethey’reup to date because measles is very contagious. It’s more contagious than COVID and can be even deadly for children and those with a compromised immune system,” said Totoraitis

Totoraitis says the vaccine is highly effective, and people who are vaccinated do not need to quarantine.

Wisconsin DHS, City of Milwaukee Health Department, Walworth County Department of Health and Human Services and the City of Milwaukee Health Department are jointly investigating.

Click here to download the WMTV15 News app or our WMTV15 First Alert weather app.

Copyright 2026 WMTV. All rights reserved.