Researchers Review the Risks of Indoor Dining

Certain activities spread the virus more effectively, Stanford study finds.

December 22, 2020

BOSTON—Scientists use the term “superspreader” destinations to describe indoor spaces where people from different households linger, share the same space and air, take off their masks, and laugh and talk. Dine-in restaurants—and other social gatherings—fit that description, but banning indoor dining is a difficult choice, the Boston Globe notes.

The restaurant industry and its workers already face financial ruin after months of drastically reduced business. Yet, some studies have shown that dining out is associated with an increased risk of coronavirus transmission.

“People talk a lot about superspreader events, but there are also superspreader destinations— types of places that are especially risky and lead to especially high rates of infection,” said David Grusky, one researcher behind a recent Stanford University study that modeled the coronavirus’s spread in indoor spaces. “One of those types of places is full-service restaurants.”

Even before states began reopening their economies, epidemiologists warned that the virus was likely to spread most rapidly indoors, and indoor dining was listed among the potentially high-risk activities that should only be resumed with extreme caution, if at all.

Since spring, emerging research has only reinforced disease experts’ initial fears. Studies have drawn on mathematical modeling, cellphone data, physics and epidemiology to find that indoor dining during the pandemic carries tremendous risk. However, restaurant dining rooms in many places remain open.

Restaurant owners have fiercely defended their businesses’ safety, emphasizing the care and cost it takes to follow restrictions, such as spacing tables at least six feet apart, seating only parties of six or fewer, limiting patrons’ dining time to 90 minutes and closing by 9:30 p.m.

In Massachusetts, contact tracers have linked 84 COVID-19 clusters to restaurants, a small fraction of the state’s 23,888 known case clusters. But scientists urge a careful interpretation of that data. Of identified clusters, nearly all—22,487 as of last week’s report in Massachusetts—are classified as “household spread,” meaning two or more people living together became infected.

That information “doesn’t really help us,” said Samuel Scarpino, a Northeastern University epidemiologist. “What we have to do is figure out how to stop [COVID-19] from getting into the households.”

Doctors know that people who live together are likely to spread the disease to one another, but the first household member was infected somewhere else, whether at work, running errands or out and about in their community.

“It’s kind of scandalizing that we have so little information [from contact tracing] about the venues of transmission this late in the pandemic,” said Marc Lipsitch, professor of epidemiology at Harvard T.H. Chan School of Public Health, adding that contact tracing’s limitations are a national and international problem.

But even state contact tracing data offers little evidence of how and where coronavirus spreads. Scarpino and Lipsitch both felt confident in saying that restaurants and indoor dining are risky.

In September, the U.S. Centers for Disease Control released a case-control study in which symptomatic people seeking COVID-19 tests were asked to list the types of places they had visited in the two weeks before getting tested. Those who tested positive were two times as likely to report having eaten at a restaurant, whether indoors or outdoors, compared with people who tested negative. No other setting showed as strong a correlation with positive cases as did restaurants, a finding that researchers attributed to the fact that eating and drinking require people to take off their masks.

Studies aside, Lipsitch said the reason indoor dining spreads COVID-19 is simple. “Uncovered, especially open, mouths, loud talking, proximity and poor ventilation are all contributors to coronavirus transmission. All of that is really clear,” he said.

Coronavirus Resources
NACS has compiled resources to help the convenience retail community navigate the COVID-19 crisis. For news updates and guidance, visit our coronavirus resources page.