Weekly Surveillance Summary

updated:

1/31/2025

Key Points

• Overall acute respiratory illness activity level remains High across Chicago. Flu activity increased from High to Very High—the maximum category; COVID-19 activity increased from Low to Moderate. RSV activity remains Moderate and is declining across all surveillance indicators.
• ED visits for flu remain significantly elevated across all age groups, as do flu hospital and ICU admissions. There has been a notable increase in severe flu cases among 5–24 year olds. ED visits, hospitalizations, and ICU admissions for RSV continue to decrease and are likely past peak for the season. Although COVID-19 ED visits have increased since last week, ICU admissions have decreased.
• The percentage of specimens that tested positive for flu is high (24%) and increasing. Almost all (99%) typed flu specimens are flu A; among those subtyped 59% have been H1N1 and 41% H3N2. Test positivity for RSV has been decreasing over the past 5 weeks. Test positivity for COVID-19 has increased slightly.
• Wastewater monitoring detected increased viral concentrations of flu A and the COVID-19 virus throughout Chicago, which are at Very High and Moderate levels compared to baseline, respectively. There was a slight decrease in average weekly RSV concentrations, but the overall level remains Very High compared to baseline.
• 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.