Key Points, updated: 2/28/2025

• Overall acute respiratory illness activity level remains Moderate across Chicago. Flu activity decreased from High to Moderate and all influenza surveillance indicators continue to decline. COVID-19 activity remains Low. RSV activity also remains Low and continues to decline across all surveillance indicators.
• ED visits and hospital admissions for flu remain elevated among all age groups but continue to decrease after peaking in late January; ICU admissions also continue to decrease. ED visits, hospitalizations, and ICU admissions for RSV continue to decrease and are past peak for the season. COVID-19 ED visits among children less than 5 years of age have increased for the past two weeks but overall ICU admissions have decreased slightly since last week.
• The percentage of specimens that tested positive for flu remains elevated (15.0%) but has decreased from a peak of 23% in January. Almost all (93%) typed flu specimens for the week are flu A; among those subtyped 72% have been H1N1 and 28% H3N2. The percentage of specimens testing positive for flu B remains low but has increased for the past five weeks. Test positivity for RSV has been decreasing since mid-December and continues to decrease. Test positivity for COVID-19 did not change from the previous week and remains low.
• Wastewater concentrations for flu A, RSV and COVID-19 remain moderate compared to baseline concentrations. Influenza B concentration levels are increasing. 
• The CDC has issued interim estimates of 2024-25 Seasonal Influenza Vaccine Effectiveness (VE) and 2024-25 COVID-19 VE, which suggest that this season’s influenza and COVID-19 vaccines were effective in preventing medically-attended illness, including hospitalization, in the US. It’s not too late to get vaccinated!
• 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.