Guide to the "Interactive Visualization of COVID-19 in Illinois"

My visualization of COVID-19 data in Illinois provides a data-forward look at COVID-19 data in Illinois. This guide will provide you an exploration of many of the graphs you can create using the visualization.

Data Source: Illinois Department of Public Health

All of the data presented on this visualization comes from the Illinois Department of Public Health’s COVID-19 website. Specifically, the data is gathered from two pages:

  1. “Restore Illinois” provides region-level data for test positivity, ICU utilization, ventilator utilization, and medical bed utilization.
  2. “COVID-19 Statistics” provides county-level data for the number of confirmed cases, deaths, and COVID-19 tests.


The “Restore Illinois” regions are based off of the Emergency Medical Services Regions, as defined in Title 77, Chapter 1(f) §515.200: Emergency Medical Services Regions. The “Restore Illinois” regions are further defined as:

The 91-DIVOC visualizations computes region totals based off of the “Restore Illinois” areas when provided county-level data.

91-DIVOC Visualization

The 91-DIVOC visualization has two major ares: the visualization and the visualization controls found below the visualization. When you first arrive at the visualization, you will see a visualization of the 7-day average of the total number of confirmed cases per day.

Data Options

In the visualization controls, the “Data” selection allows you view various different data about COVID-19 in Illinois. Currently, the following data choices are available:

  1. Confirmed COVID-19 Cases, reporting the total number of people in Illinois who has received a positive COVID-19 test.
  2. Confirmed COVID-19 Deaths, reporting the total number of deaths confirmed to be caused by COVID-19.
  3. COVID-19 Tests, reporting the total number of COVID-19 tests administered.
  4. Test Positivity, the percentage of tests administered that returned a positive result.
    • This value can be computed approximately by taking the number of confirmed cases divided by the total number of tests.
    • The Illinois Department of Health also provides this value at a region-level.
  5. ICU Utilization, reporting the capacity of Intensive Care Units (ICUs).
  6. Ventilators in Use, reporting the use of available ventilators.
  7. Medical Beds in Use, reporting the use of medical/surgical beds in hospitals.

Restore Illinois Phase 3/Phase 4 Threshold

On the “Restore Illinois” page, the Department of Health shows gauge visualization of six factors including test positivity, ICU utilization, ventilator use, and medical/surgical beds. When viewing those charts, displays this gauge as a dashed red line showing when the gauge would reach the “Phase 3” threshold.

Highlight Options

In the visualization controls, the “Highlight” selection allows you view various data on different regions and counties across Illinois.

Additional Highlights

It is often useful to highlight multiple counties to compare case data between various counties. Towards the bottom of the visualization controls, the “+Add Additional Highlight” allows you to highlight multiple regions/counties at once. For example, we can compare the number of tests administered in Lake County vs. Cook County or the test positivity of Cook and Lake Counties:

Normalized by Population

All data presented can be viewed either as raw numbers (the first visualization displayed) or normalized by the county population (the second visualization displayed). In both visualizations, the same data is displayed except that the normalized data is divided by the county population. The normalized data is then presented as per 1,000,000 people.

As an example, consider the testing data of both Cook County (Illinois’ largest county, containing Chicago) and Champaign County (a mid-sized county, containing the University of Illinois at Urbana-Champaign).

This normalized view of the data allows each county to be compared in a way that focuses on how each individual person in the county is doing and provides a good county-to-county comparison.

Show Options

Behind the highlighted data, other data is shown slightly faded to provide greater prospective on the highlighted data. By default, the highlighted data is displayed along with the “Top 25” counties in Illinois. There are several different options to choose by controlling the “Show” options in the visualization controls:

Many More Options

This guide only begins to explore the different options available. Additional options include:

Finally, every change you make to the visualization will generate a “Direct Link” that will link to the specific visualization you have created. You can bookmark this link to view it later or share it with friends/family to help them understand COVID-19 data.

View It -- Interactive Visualization of COVID-19 in Illinois >>