Key Points, updated 5/23/2025

• Week 20 (May 11–17, 2025) marks the final week of the influenza surveillance season. The Respiratory Virus Surveillance PDF report distributed via the HAN will resume its weekly publication in October 2025. The Respiratory Illness Dashboard will continue to be updated weekly and will highlight key relevant information. 
• Overall acute respiratory illness activity level in Chicago remains Minimal. Flu activity remains Low; COVID-19 and RSV activity remain Minimal.  
• ED visits, hospitalizations, and ICU admissions for flu, RSV, and COVID-19 remain low across all age groups. 
• Test positivity rates for influenza, RSV, and COVID-19 remain low. However, in the past two seasons, COVID-19 test positivity has tended to rise during the summer months. Refer to the Respiratory Illness Dashboard for updates.
• The percentage of specimens testing positive for rhinovirus/enterovirus has been rising since March but showed a slight decline last week, aligning with typical seasonal patterns observed in previous years.
• Overall wastewater concentrations for RSV remain minimal and COVID-19 has increased from minimal to low. Flu A and Flu B concentrations remain low.  
• 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. 
• For information on the national bird flu outbreak, see the CDPH H5N1 Bird Flu webpage and the CDPH HAN: Flu Page for clinicians.