Areas in the United States that do not adhere to any social distancing policies face 35 times more cases of the novel coronavirus, according to a study published Thursday in a peer-reviewed health-care journal.

The study, published in the journal Health Affairs, looked at the policies mandating social distancing, and found that the longer a measure was in effect, the slower the daily growth rate of COVID-19, the virus’s disease. Researchers from the University of Kentucky, University of Louisville and Georgia State University looked at confirmed coronavirus cases in the United States between March 1 and April 27, totaling about 1 million reported instances at the time, illustrating “the potential danger of exponential spread in the absence of interventions.”

For social distancing policies that lasted at least 16 to 20 days, the daily rate of infection dropped by more than 9 percentage points, according to the study. Policies lasting 15 days and less also saw declines in the daily infection rate, researchers found. Such social distancing measures, mandated by 95 percent of the country, include shelter-in-place orders, school closures, bans on large events and the closure of gyms, bars and restaurants.

Places with no social distancing orders were at substantially higher risk for infection.

“Holding the amount of voluntary social distancing constant, these results imply 10 times greater spread by April 27 without [shelter-in-place orders] . . . and more than 35 times greater spread without any of the four measures,” the researchers wrote in “Strong Social Distancing Measures in the United States Reduced the COVID-19 Growth Rate.”

The findings come as more states start the process of reopening, easing restrictions and social distancing guidelines. While social distancing has kept more Americans healthy, some states are already weeks into lifting restrictions.


Even as leading health experts say the “consequences could be really serious” if states move too quickly to reopen, anti-lockdown protesters have swarmed streets and state capitols in recent weeks. In Wisconsin, hours after the state Supreme Court threw out the state’s stay-at-home order on Wednesday, residents flooded the bars and flouted social distancing, The Washington Post reported.

On Thursday, the Centers for Disease Control and Prevention issued a set of minimal recommendations to help guide schools, businesses and other facilities into the next phase of the coronavirus pandemic. There are now more than 1.4 million confirmed coronavirus cases in the United States and at least 85,000 deaths.

The researchers wrote that the study did not look at actual social distancing but at whether the presence of government restrictions encouraging social distancing reduced spread when compared to simply “providing information and recommendations.”

Charles Courtemanche, an associate professor of economics at the University of Kentucky, and four co-authors noted the limitations of the study. The researchers pointed to how the number of coronavirus cases are “known to understate the true prevalence of the disease, as they do not include asymptomatic carriers, those who are not ill enough to seek medical care, and those who are unable to obtain a test due to supply constraints.”

They expressed hope that the research will provide lawmakers a resource on the benefits of social distancing as states decide how they reopen their respective economies.

“Further research is needed as gradual, untested steps toward reopening are taken across the country,” the researchers concluded.

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