Active Public Health Outbreaks in Wisconsin: Comprehensive Report
Executive Summary (November 2025)
As of late November 2025, Wisconsin is managing several active public health challenges. While the massive Pertussis (Whooping Cough) surge of 2024 has begun to taper, case numbers remain elevated compared to historical baselines. A concentrated Measles outbreak in Oconto County earlier this year has largely stabilized, though surveillance remains high due to declining vaccination rates.
Concurrently, state epidemiologists are monitoring emerging threats, including a suspect case of infant botulism linked to a national formula recall and seasonal increases in respiratory viruses.
Current Outbreak Status
Pertussis (Whooping Cough)
Wisconsin continues to grapple with the tail end of a significant Pertussis outbreak that peaked in 2024. While 2023 saw only 51 cases statewide, 2024 witnessed an explosive increase to nearly 2,000 cases. In 2025, the transmission has slowed but remains persistent, with 659 confirmed cases reported as of late October.
Demographic Impact: The outbreak has disproportionately affected adolescents. Approximately 50% of cases in 2025 have been identified in children aged 1–10 years, a shift from the 2024 trend which heavily impacted the 11–18 age group.
Case Count Comparison
Data reflects confirmed cases reported by WI DHS.
Measles Surveillance
Earlier in 2025, Wisconsin confirmed 36 cases of measles, all localized within Oconto County. This cluster represents a significant deviation from the state's typical near-zero baseline. As of November 2025, health officials have declared the immediate outbreak contained, with no new cases expected from this specific chain of transmission.
Contrasting Viewpoints: Vaccination Rates
While state officials emphasize that the immediate risk is low, independent health analysts and news sources point to a concerning root cause: a 5-point decline in MMR vaccination rates over the last eight years. Oconto County, the epicenter of the 2025 cluster, has seen vaccination rates drop to 87%, below the threshold typically required for herd immunity. This suggests that while the current outbreak is over, the state remains vulnerable to future clusters.
Foodborne & Environmental
- Infant Botulism Wisconsin DHS is currently investigating one suspect case linked to a multistate outbreak involving ByHeart Whole Nutrition infant formula. The infant is hospitalized. This is part of a larger national recall.
- Salmonella (Pet Geckos) Two laboratory-confirmed cases in Wisconsin have been linked to a multistate outbreak of Salmonella associated with pet geckos.
- Salmonella (Eggs) A major outbreak linked to Milo's Poultry Farms in Bonduel, WI, which sickened dozens in late 2024, is now largely resolved, though legal and regulatory follow-ups continue into 2025.
Respiratory Virus Trends
Activity is currently low but showing a slow, steady seasonal increase. Primary strain: Influenza A (H3).
Wastewater surveillance indicates very low levels with a slow upward trajectory typical for late autumn.
Hospitalization rates remain below baseline, though pediatric monitoring is active.