Flu season in Midwest: Long, cold winters mean sustained peaks and strained hospital systems
The Midwest doesn't get the most dramatic flu spikes, but it gets some of the most sustained ones. A January peak here doesn't resolve in two weeks — it can stay elevated through February, grinding down hospital capacity and keeping ERs busy for six or seven consecutive weeks. The mechanism is straightforward: five months of winter mean five months of indoor crowding, and Chicago's role as the country's central transit hub means new strains cycle through the region continuously once a season gets going.
Current flu activity — HHS Region 5
This data is pulled live from the Delphi CMU Epidata API, which mirrors CDC FluView ILINet data for HHS Region 5. It reflects the most recent week available — typically data through the prior Saturday, published by the CDC the following Thursday.
States in HHS Region 5
HHS Region 5 covers Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin. These states are grouped together by the Department of Health and Human Services for federal health program administration, and the CDC uses the same regional boundaries for flu surveillance reporting. ILI activity data is aggregated across all ILINet providers in the region, so the number reflects the regional average — individual states can vary significantly.
When flu typically peaks here
HHS Region 5 typically peaks in January, close to the national average but with a longer shoulder on both sides. Activity often starts building in November, reaches its high point in the second or third week of January, and doesn't fall below Moderate until late February in most years.
Minnesota is consistently the most active state in the region, running a week or two ahead of the regional average and hitting higher ILI peaks than its population size would suggest. The combination of extreme cold, a large immigrant population from flu-endemic countries, and a relatively young workforce contributes to faster spread when a season gets going.
Michigan often lags the rest of the region by one to two weeks, with Detroit showing activity close to the Chicago timeline but the Upper Peninsula running significantly later due to isolation and lower density. In years when the Upper Peninsula finally sees a spike, it's often March.
What drives Midwest flu patterns
Extended cold season. The Midwest has the longest sustained cold season of any major population center in the country. From November through March, temperatures consistently drive people indoors — schools, offices, shopping centers, and homes with shared air handling. The flu virus doesn't just peak here; it has optimal conditions for months.
Chicago as a transit hub. O'Hare International is the second-busiest airport in the US and the main hub for the Midwest. Chicago's L trains carry 700,000 daily riders. The city's role as the region's commercial center means strains introduced anywhere in the Midwest tend to cycle through Chicago and back out to surrounding areas within weeks.
Industrial city demographics. Detroit, Cleveland, Toledo, Gary, and other legacy industrial cities have older populations, higher rates of underlying conditions, and — in some cases — healthcare systems that are still recovering from decades of economic stress. Flu hospitalizations per capita in these cities often run above the regional average even in moderate seasons.
Wisconsin and Minnesota's dairy/agricultural communities. Rural agricultural communities in Wisconsin and Minnesota create a different transmission environment: tighter extended-family networks, shared equipment and facilities, and lower average healthcare access than urban areas. When flu hits a rural Wisconsin county, it can burn through faster than the ILI data shows because fewer people seek care.
Recent seasons in HHS Region 5
Regional peak timing and severity can vary substantially from the national picture. The table below shows Region 5-specific peak months and severity for recent seasons, based on CDC FluView regional ILI data.
| Season | Regional peak | Dominant strain | Severity | Notable |
|---|---|---|---|---|
| 2024–25 | January | H3N2 / H1N1 | High | Above-average; sustained elevated activity through February |
| 2023–24 | January | H1N1 | Moderate | Moderate; Minnesota peaked a week ahead of regional average |
| 2022–23 | December–January | H3N2 | High | Early onset; Chicago showed surge before Christmas |
| 2021–22 | February | H3N2 | High | Late, compressed season; unusually sharp peak for Region 5 |
| 2019–20 | January | H1N1 | High | Strong season; Upper Peninsula lagged by ~3 weeks |
If you're in the Midwest and the season is at High, plan on it staying there for 4–6 weeks. Midwest flu seasons are characterized by sustained elevation rather than sharp spikes — the peak is broad and flat rather than pointed. Stock up on rapid tests, not just for the peak week, but for the entire plateau. Track current activity. →
How to use this data
The live activity level above reflects the most recent week of CDC ILINet data for Region 5. There is always roughly a one-week lag between real-world conditions and published numbers — providers report weekly, the CDC publishes Thursdays, and this page reflects those numbers. During a rapidly rising season, treat the current level as a floor.
The ILI percentage is the share of outpatient visits attributed to influenza-like illness across all ILINet reporting providers in the region. It is not a case count and does not capture people who don't seek care. In regions with lower healthcare utilization rates (rural areas, communities with limited access), ILI percentages tend to understate true community activity.
For the most complete picture of the current season — including strain typing, lab positivity trends, and hospitalization data — the IsItFluSeasonYet homepage shows all of this in context. The regional activity shown here is the same data source as the homepage's region breakdown.