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Study Finds Social Distancing Slowed U.S. Growth of COVID-19

In This Article

  • Between March 10 and March 25, 2020, all 50 U.S. states and D.C. enacted at least one statewide physical distancing measure to help stop the spread of COVID-19
  • A study led by Massachusetts General Hospital clinicians found that those physical distancing orders led to an estimated reduction of 600,000 cases within three weeks of implementation
  • Although physical distancing has been proven effective in reducing the spread of SARS-CoV-2, the researchers suggest that continued and further containment measures are necessary to curb the ongoing spread

According to a study led by Massachusetts General Hospital clinicians, published in PLOS Medicine, government-issued social distancing orders significantly slowed the spread of COVID-19 in the United States after state implementation.

Mark J. Siedner, MD, MPH, clinician in the Division of Infectious Diseases at Mass General, Alexander Tsai, MD, PhD, a researcher and associate director for trainee development in the Chester M. Pierce Division of Global Psychiatry at Mass General, and colleagues reported that statewide physical distancing measures—which were enacted in all 50 states and the District of Columbia—led to an estimated reduction of more than 600,000 cases within three weeks of implementation.

By comparing changes in COVID-19 cases and COVID-19-attributed deaths before and after the implementation of distancing orders, researchers confirmed that the average daily COVID-19 case growth rate began declining approximately one incubation period (i.e., four days) after implementation of the first statewide physical distancing measures. They also reported a decline in the COVID-19-attributed death rate after implementation, which had not been analyzed previously.

The model suggests that by one week after implementation, the measures reduced the total number of reported cases by approximately 1,600 cases, and by three weeks after implementation, approximately 621,000 cases—due to the exponential growth of the spread.

While the implementation of distancing orders may have given health care leaders more time to coordinate a response to the outbreak, Dr. Tsai said that a delayed national response still contributed to more cases, noting that "much of the time before these local measures were implemented was simply wasted."

Dr. Siedner emphasized that although distancing has been proven to reduce the spread of COVID-19, it will likely be necessary to implement further measures in order to combat the virus, especially considering that cases are still trending upwards.

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