Wisconsin measles total reaches 267 as new county clusters emerge

New probable cases in Rock County and confirmed infections in Marathon and Chippewa counties are widening Wisconsin’s measles outbreak, with 99.3% of confirmed cases among unvaccinated people.

Wisconsin health officials have confirmed new measles outbreaks in several counties, pushing the state’s total to 267 confirmed cases as the virus continues to spread among largely unvaccinated residents. The Wisconsin Department of Health Services said the latest figures include probable cases in Rock County and new confirmed infections in Marathon and Chippewa counties.

In Rock County, officials are tracking five probable cases that appear to be connected, although investigators have not yet identified where the infection began. The cases are considered probable because they match measles symptoms, but they have not been verified through laboratory testing. Health officials in the county said they are still trying to determine whether the cluster is linked to a wider chain of transmission.

Marathon County has reported six new confirmed cases, while Chippewa County has 11 confirmed cases tied to travel outside the state. Public health teams in both counties are working to identify people who may have been exposed. Officials have said these infections are separate from the major outbreak in south-western Wisconsin, which continues to affect Grant, Iowa, Lafayette and Vernon counties.

According to the state health department, that larger outbreak now accounts for 237 confirmed cases and six probable cases. Across Wisconsin, 265 of the 267 confirmed infections, or 99.3%, have been in people who were not vaccinated. Five people have been hospitalised, underscoring the risks posed by a disease that is highly contagious but largely preventable with two doses of the MMR vaccine. Health officials continue to urge families to check their immunisation records and make sure they are up to date.