Key Points, updated: 3/7/2025

• Overall acute respiratory illness activity level remains Moderate across Chicago. Flu activity remains Moderate, and all influenza clinical 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 for flu remain elevated among all age groups.  Both ED visits and hospital admissions attributable to the flu continue to decrease from the late January peak. ED visits, hospitalizations, and ICU admissions for RSV continue to decrease and have passed their peak for the season. ED visits for COVID-19 have decreased or remained the same over the past week across all age groups, and ICU admissions have continued to decrease over the last two weeks.
• The percentage of specimens that tested positive for flu remains elevated (11%) but has decreased from a peak of 23% in January. The majority (77%) of all typed flu specimens for the week were flu A; however, the proportion of specimens positive for flu B has continued to increase over the last 6 weeks. Among flu A that were subtyped 67% have been H1N1 and 33% H3N2. 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.
• Wastewater concentrations for flu A and COVID-19 have increased from moderate to high, and RSV concentrations have remained moderate compared to baseline concentrations. Influenza B concentration levels are also moderate.
• 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.