Chicago COVID-19 Cases and Tests by ZIP Code - Historical

Historical data tracks COVID-19 cases, tests, and deaths for Chicago residents by home ZIP code. Cases are counted based on the week the test specimen was collected, and test counts include multiple tests per person. Data originates from the Illinois National Electronic Disease Surveillance System, Cook County Medical Examiner’s Office, and other public health sources.

Use Cases

• Analyze weekly case counts by ZIP Code to identify neighborhood-level infection trends over time.
• Calculate Percent Tested Positive metrics to compare positivity rates across different ZIP Codes, noting data limitations.
• Investigate the relationship between cumulative deaths and case counts at the ZIP Code level for mortality analysis.
• Map ZIP Code data to Chicago Community Areas using provided crosswalks for broader geographic public health studies.

Strengths

• Data is sourced from authoritative public health systems including the Illinois National Electronic Disease Surveillance System.
• Includes detailed methodological notes on case and test counting, such as the inclusion of multiple tests per person after 10/29/2020.
• Provides a crosswalk to Chicago Community Areas for geographic comparison and aggregation.

Limitations

• The dataset is retired and marked as historical-only, indicating it is no longer updated with current data.
• Test counts are noted as likely underestimates due to the phased onboarding of electronic lab reporting and shifts in testing availability.
• Case counts for ZIP Codes with fewer than five cumulative cases are suppressed for privacy, preventing complete aggregation.

Provenance

Source

Illinois National Electronic Disease Surveillance System, Cook County Medical Examiner’s Office, Illinois Vital Records, American Community Survey (2018)

Collection Method

Cases counted based on week of specimen collection; tests counted based on week of specimen collection and include multiple tests per person.

Time Range

Tests from 3/1/2020 onward.

Freshness

Historical-only; last updated 2026-02-22.

Geography

Chicago residents only, based on home ZIP Code.