Weekly Surveillance Summary -
Key Points

updated: 2/21/2025

• Overall acute respiratory illness activity level remains Moderate across Chicago. Flu activity remains High although all influenza surveillance indicators decreased slightly from last week. COVID-19 activity remains Low. RSV activity also remains Low and continues to decline across all surveillance indicators.
• ED visits and ICU admissions for flu remain elevated among all age groups, especially among those <18 years of age, but have decreased. ED visits, hospitalizations, and ICU admissions for RSV continue to decrease and are past peak for the season. COVID-19 ED visits and ICU admissions have increased slightly since last week. 
• The percentage of specimens that tested positive for flu remains elevated (16.0%), but has decreased from a peak of 23% in January. Almost all (95.3%) typed flu specimens for the week are flu A; among those subtyped 69% have been H1N1 and 31% H3N2. The percentage of specimens testing positive for flu B remains low but has increased for the past four weeks. Test positivity for RSV has been decreasing since mid-December and continues to decrease. Test positivity for COVID-19 has decreased slightly from the previous week and remains low. 
• Wastewater concentrations for flu A and RSV decreased from high to moderate compared to baseline, and COVID-19 decreased from moderate to low compared to baseline concentrations. 
• Flu and COVID-19 vaccine coverage across the city remain low. See CDPH’s Mid-Season Seasonal Respiratory Vaccine Coverage Report for more details.
• For information on the national bird flu outbreak, see the CDPH H5N1 Bird Flu webpage and the CDPH HAN: Flu Page for clinicians.