Study says partial openings can help reduce COVID — but full reopening could lead to hundreds of thousands of infections

Researchers from Northwestern and Stanford used cell phone data and computer models to analyze where 98 million people visited during the early months of the pandemic.

SHARE Study says partial openings can help reduce COVID — but full reopening could lead to hundreds of thousands of infections

Reopening a business at 20 percent of its maximum occupancy can cut down on infections by 80 percent compared with a full reopening, study finds.


Restricting occupancy at restaurants, churches, stores and other public places is one of the most effective ways to reduce the spread of COVID-19, new research finds.

But fully reopening restaurants could lead to hundreds of thousands of new infections in Chicago alone, the research released Tuesday by the journal Nature found.

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Using cellphone data and computer models that study where 98 million people visited nationwide during the early months of the pandemic, researchers at Northwestern University and Stanford found a small number of “superspreader” locations account for a large majority of infections and also help explain the disproportionate number of infections in Black and Latino communities.

Analyzing infection numbers recorded in March and April as well as mobility patterns of people, researchers estimated that if restaurants had fully reopened here in May, there could have been 600,000 additional virus cases.

“On average across metro areas, full-service restaurants, gyms, hotels, cafes, religious organizations, and limited-service restaurants produced the largest predicted increases in infections when reopened,” the study says. “Reopening full-service restaurants was particularly risky: in the Chicago metro area, we predicted an additional 596k infections by the end of May, more than triple the next riskiest” category. 

“Reopening full-service restaurants has the largest predicted impact on infections, due to the large number of restaurants as well as their high-visit densities and long dwell times,” the study said. 

That finding gives ammunition to Gov. J.B. Pritzker who has called restaurants superspreader sites for the virus and defends his decision to ban indoor dining. 

“Places where people gather and spend time together without masks are places where there is increased risk of contracting coronavirus,” Pritzker spokeswoman Jordan Abudayyeh said in an email.

But the study also stated that reopening a business in Chicago at 20 percent of its maximum occupancy can cut down on infections by 80 percent compared with a full reopening. 

Beth Redbird, a study co-author and assistant professor of sociology at Northwestern, said the research aims to provide policy makers with ways to address the disparities seen in low-income communities of color that are experiencing high rates of infections. 

Low-income neighborhoods tend to have small grocery stores, for instance, that can pack in more people in tighter areas, Redbird said. Policy makers could address that issue by helping to broaden the option for these communities to have more shopping options, she added. 

Public places, including government services, can offer options such as drive-through locations, she said. In general, any options to increase spacing and ventilation can address risk.

While the researchers discourage full reopenings of businesses, reduced capacity can be an important component, Redbird added.

“There are policy remedies that are not all or nothing,” she said. 

“The idea behind the project is understanding that with a virus like COVID, that human movement can inform policy around reducing infection,” Redbird added.

Brett Chase’s reporting on the environment and public health is made possible by a grant from The Chicago Community Trust.

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