GRANT COUNTY, Wis. — Wisconsin’s measles outbreak surged again during the week ending October 30, 2026, pushing the state’s total for the year to 392 cases and keeping southwestern Wisconsin at the center of the outbreak.

The statewide count jumped sharply on October 30, 2026, passing 300 only one week earlier. Federal data summarized October 30, 2026, showed 82 new cases in Wisconsin during the past week, bringing the state total to 392. Of those cases, 336 — about 86 percent — have been confirmed in Grant, Iowa, Lafayette, and Vernon counties in southwestern Wisconsin, the region where the outbreak began.

The outbreak dates to early July 2026, although it was not publicly reported until August 2026. Since then, cases have spread beyond the southwest corner of the state. The October 30, 2026, update added a case in Marquette County, the first case reported there. According to the Wisconsin Department of Health Services, that case involved a person who acquired measles through out-of-state travel and is not tied to the other cases in the state.

Other counties outside the southwest outbreak have also reported cases linked to travel rather than local spread, including Chippewa County, which has 33 infections, according to the federal summary. Cases have additionally been reported in Rock, Richland, Jackson, and Marathon counties.

The pattern of who is getting sick has stayed consistent through the outbreak. Of Wisconsin’s 392 cases in 2026, all but three have been in people who had not received the measles, mumps, and rubella vaccine, according to state health officials. The vaccine is 97 percent effective at preventing illness.

State and county officials in southwestern Wisconsin are working to identify and notify people who may have been exposed to the virus, the Department of Health Services said. Wisconsin residents can check their own measles, mumps, and rubella vaccination status through the Wisconsin Immunization Registry at dhfswir.org.

Grant County’s current case count within the new 392 total was not broken out in the October 30, 2026, reports, and that detail remains pending. Earlier in the fall, Grant County health staff cautioned that the county’s reported count likely understated the true number of infections, because not everyone who gets sick is tested, seeks medical care, or contacts a public health agency.

For tri-state readers, the practical point is close to home: the outbreak’s core remains in the counties just across the Mississippi River from Dubuque, and the state total is now within eight cases of 400.

Sources: Milwaukee Journal Sentinel, October 30, 2026; CIDRAP summary of Centers for Disease Control and Prevention data, October 30, 2026; Wisconsin Department of Health Services, October 2026 updates.