Current data quality grade
To help the public understand how well each state is performing, we have assigned each state a data-quality grade based on our assessment of the completeness of their reporting. Learn more
On June 1, 2020, Massachusetts began to report probable cases and probable deaths, causing *Total cases and Total deaths to appear to increase sharply in our data.
On June 30, 2020, Massachusetts decreased the number of cumulative hospitalizations and confirmed and probable deaths "due to ongoing data cleaning which identifies and removes duplicate reports."
On July 31, 2020, Massachusetts noted that "Delays in the reporting of test results to DPH from multiple laboratories, including large national commercial laboratories, are reflected in today’s case counts. However, these positive test results have been assigned retrospectively to the appropriate date of test." We will backfill case data for Massachusetts in the near future.
On August 12, 2020, Massachusetts began reporting probable cases weekly instead of daily. This can lead to apparent spikes in the data when the weekly numbers are incorporated, as happened on August 19. Beginning August 20, 2020, we will use the daily total case count from the race and ethnicity section of the dashboard, which includes both confirmed and probable cases, and will backfill the previous week's case counts.
On August 31, 2020 we updated Massachusetts' Total PCR Tests (specimens) before August 12, 2020 based on the state's "Tests by Date" dataset, extending the column back to January 22, 2020.
On September 2, 2020, MA reported that it had shifted to using the more restrictive August 6 definition of probable cases released by the CSTE. This change caused a significant decrease in several data points where probable cases or probable deaths were included, particularly the overall case count, which dropped by more than 7,000. Historical data was also affected.
As of September 11, 2020, Massachusetts’ total test results reflect total specimens. The number of unique people tested is available in our API as
Negative test results reported in our API and CSVs are calculated by subtracting Positive PCR tests (people) from Total PCR tests (people).
New tests (Calculated)Total PCR tests (specimens)
New deaths (Calculated)
- Sep 2: On September 2, 2020, Massachusetts reported that it had shifted to using the more restrictive August 6 definition of probable cases released by the CSTE. This change caused a significant decrease in several data points where probable cases or probable deaths were included, particularly the overall case count, which dropped by more than 7,000. Historical data was also affected.
We calculate daily changes based on the data states report each day. Some states report new cases, tests, and deaths using other methods. Please consult official state data sources for more information. We chart “New tests” using different units across jurisdictions, because not all states and territories report tests in the same units. Learn more about total test units and see what we chart for each jurisdiction in our total tests documentation.
We do not have a complete dataset for every metric in every state. If we we have data for less than 30% of the past 90 days for a given metric, you’ll see a warning instead of a chart for that metric.
All the data for these charts is available for download. You can also review tabular national data on our US historical data page and data for each state and territory on the individual state or territory’s overview page.
Viral (PCR) testsHistorical data for viral (PCR) tests
(in test encounters)