When Illinois reports no data, several days of data, or unusual data (such as decreases in values that should increase), our volunteers note it here on the date the anomaly occurred. We also note here changes in our own methodology that affect the data.
Negative test results reported in our API and CSVs are calculated by subtracting Total cases from Total PCR tests (specimens) in the absence of better data.
On November 6, 2020, Illinois announced that they "will report confirmed cases and probable cases combined.” Due to this we cannot continue reporting Confirmed and Probable cases separately, however the time series for these metrics are available in the historical data, and our data downloads.
As of October 15, 2020, Illinois combines PCR and antigen tests in the total tests figure reported on the state's dashboard.
On September 4, 2020, Illinois reported over 140,000 new Total PCR tests (in specimens) and over 5,000 new Cases. According to the Chicago Tribune, "The Illinois Department of Public Health said Friday there was significant slowdown in the agency's test reporting earlier this week that it is just catching up with."