Inpatient, Emergency Department, and Outpatient Visits for Respiratory Illnesses

Use caution when comparing data between these two time periods due to data suppression differences between the two ESSENCE instances. The CDC National Syndromic Surveillance Program (NSSP) utilizes diagnostic codes and clinical terms to create definitions for diagnosed COVID-19, influenza, RSV, and acute respiratory illness. For more information on diagnostic codes and clinical terms used, visit: cdc.gov/nssp/php/onboarding-resources/companion-guide-ed-data-respiratory-illness.html and cdn.ymaws.com/www.cste.org/resource/resmgr/pdfs/CDC_Broad_Acute_Respiratory_.pdf.

The data is characterized by selected demographic groups including age group and race/ethnicity. The dataset also includes percent of weekly outpatient visits due to ILI as reported by several outpatient clinics throughout Chicago that participate in CDC’s Influenza-like Illness Surveillance Network (ILINet). Finally, weekly respiratory illness activity levels for influenza, COVID-19, RSV and broad acute respiratory illness (also referred to as acute respiratory illness or ARI) are included in the dataset for emergency department visits from MMWR Week 202427 (week starting 6/30/2024) forward.

Respiratory illness activity levels are an indication of how much people are seeking healthcare in emergency departments for a broad range of respiratory illnesses. This metric is calculated by using the percentage of emergency department visits for influenza, RSV, COVID-19, and ARI and comparing the percentage to times in the past when visits were low. ARI is used as an overall indicator and includes diseases like influenza, COVID-19, and RSV along with the common cold, pneumonia, and other diseases and symptoms of acute respiratory illness.

Five activity levels range from minimal to very high. For more information on respiratory illness activity levels, see cdc.gov/respiratory-viruses/data/activity-levels.html#cdc_data_surveillance_section_7-data-notes. For more information on ESSENCE, see dph.illinois.gov/data-statistics/syndromic-surveillance For more information on ILINet, see cdc.gov/fluview/overview/index.html#cdc_generic_section_3-outpatient-illness-surveillance All data are provisional and subject to change.

Information is updated as additional details are received. At any given time, this dataset reflects data currently known to CDPH. Numbers in this dataset may differ from other public sources.