This illustration, created at the Centers for Disease Control and Prevention (CDC), reveals ultrastructural morphology exhibited by coronaviruses. Note the spikes that adorn the outer surface of the virus, which impart the look of a corona surrounding the virion, when viewed electron microscopically. A novel coronavirus, named Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), was identified as the cause of an outbreak of respiratory illness first detected in Wuhan, China in 2019. The illness caused by this virus has been named coronavirus disease 2019 (COVID-19).

Internal data on COVID-19 outbreaks in Illinois — prepared by the state health department and covering four different days between July and September — was obtained by the Documenting COVID-19 project at Columbia University’s Brown Institute for Media Innovation and the Midwest Center for Investigative Reporting as part of an open-records request. It gives detailed information and case counts for nearly 2,600 separate outbreaks across the state. 

Read the story that accompanies this database here.

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Data methodology: To analyze the data, four separate summary files of coronavirus outbreaks — point-in-time reports covering July 24, Aug. 17, Sept. 1 and Sept. 30 from the Illinois Department of Public Health — were imported and duplicate entries were removed. Entries with blank or “Not a Case” statuses were excluded, leaving only entries with “Confirmed,” “Probable” or “Suspect” case counts. A total of 812 duplicate rows were removed across all four files before they were merged, leaving 2,599 separate outbreak entries. Regional narrative summaries and other detailed case information are not included in this release. The names of outbreaks as described by Illinois Department of Public Health are unedited and may contain spelling and other errors.

The Documenting COVID-19 project at Columbia University’s Brown Institute for Media Innovation is a collaborative FOIA journalism effort to compile newsworthy records and data related to the coronavirus pandemic. For more information, email

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