Illinois Flu Activity This Week
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Track current flu activity in Illinois with weekly CDC surveillance data. This page shows Illinois influenza levels, historical trends, and how Illinois compares to nearby states and the national average. Data is sourced from the CDC's ILINet network and updated every Friday.
Key Takeaways
- 1 Flu activity in Illinois is currently LOW, with 1.6% of outpatient visits for flu-like illness.
- 2 Activity has been relatively stable over recent weeks.
- 3 Illinois flu activity is below the national average of 2.9%.
CDC Recommendations at This Level
Flu activity is low — good time to prepare
- • Get your flu vaccine if you haven't this season — it takes 2 weeks to build full protection
- • Stock up on basics: fever reducers, tissues, electrolyte drinks
- • Normal daily routines are fine — no special precautions needed right now
This is general public health guidance based on CDC recommendations — not personal medical advice. Talk to your healthcare provider about what's right for you and your family.
Illinois Flu Trend — 2025-2026 Season
ILI = influenza-like illness. Percentage of outpatient visits for ILI symptoms.
Is Flu Getting Better or Worse in Illinois?
Flu is declining in Illinois
Good news — flu activity is going down. Based on CDC forecasting data, each case is leading to fewer new cases, which means you should see continued improvement in the coming weeks.
Technical details (CDC Rt estimate)
Reproduction number (Rt): 0.88 (95% CI: 0.75 – 0.96)
Probability of growth: 1%
Rt below 1.0 means each case leads to fewer new cases (declining). Above 1.0 means growing.
Based on CDC forecasting data as of March 31, 2026. Source
Illinois vs. National Average and Nearby States
Nearby States
Sources & Methods
ILI (influenza-like illness) is defined as fever plus cough or sore throat. Data reflects the percentage of outpatient visits for ILI reported through the CDC's ILINet surveillance network. Activity levels are computed from ILI percentage thresholds. Learn more about our methods .
More Health Data for Illinois
Cities in Illinois
Flu data available for these Illinois cities:
Frequently Asked Questions
Is the flu going around in Illinois right now?
Based on the latest CDC data, flu activity in Illinois is currently low. 1.6% of outpatient visits are for flu-like illness. This data is updated weekly from the CDC's ILINet surveillance network.
What are current flu levels in Illinois?
Illinois's current influenza-like illness (ILI) rate is 1.6%, classified as low activity. ILI measures the percentage of outpatient visits where patients present with fever plus cough or sore throat — the standard CDC metric for flu surveillance across all 50 states.
How does Illinois flu activity compare to the national average?
Illinois's flu activity is 1.3 percentage points below the national average. The nearby states table shows how Illinois ranks regionally.
What does the flu activity level mean for Illinois?
The activity level indicates how much flu-like illness is being reported in Illinois compared to typical levels. "High" means more people are visiting doctors with flu symptoms than usual. It does not indicate the severity of the flu viruses circulating.
Where does this flu data come from?
This data comes from the CDC's ILINet (Influenza-like Illness Surveillance Network), accessed via the Delphi Epidata API. ILINet includes reports from thousands of healthcare providers across the United States who track the percentage of patient visits for flu-like symptoms each week.
How often is this page updated?
This page is updated weekly, typically on Fridays after the CDC publishes new FluView data. The data usually reflects activity from the previous week, so there is a one-to-two week delay between when illness occurs and when it appears here.
Is flu getting better or worse in Illinois?
Based on the CDC's reproduction number (Rt) estimate, flu in Illinois is declining with an Rt of 0.88. This means each flu case is generating fewer than one new case on average, so activity should continue to decrease. There is a 1% probability that flu is growing.
Local Health Signal is not affiliated with the CDC or any government agency. Data is provided for informational purposes only and is not intended for clinical decision making. See our methods page for details on data sources and limitations.