Study shows restaurants site of most covid cases

SANTA FE — Research published this month takes aim at a question New Mexico and other states are wrestling with: Where are all these COVID-19 infections happening?

A peer-reviewed paper in the journal Nature suggests a small number of “superspreader” environments drive most of the infections — with full-service restaurants by far the riskiest locations.

But the authors also said that even partly limiting capacity at certain “points of interest” — such as restaurants, gyms and similar nonresidential locations — can have an outsized impact on infections.

Their predictive model, for example, showed that limiting capacity to 20% at these destinations in the Chicago area would cut down on new infections by more than 80%, even though customer visits would fall only 42%.

New Mexico Human Services Secretary David Scrase highlighted the research when the state announced a host of new restrictions on in-person business activity.

The state’s new health order imposes a 25% capacity limit on groceries and retail stores that are deemed essential and religious establishments while entirely banning on-site dining at restaurants. The restrictions are set to expire Nov. 30, though they may be renewed or relaxed after that, perhaps county by county.

In an interview Wednesday, Scrase suggested the new research matches what New Mexico policymakers had already figured out — that closed, crowded and close-contact settings are the most risky places for spread of the disease.

But the paper offered evidence, he said, on the power of occupancy limits — a strategy he described as more akin to a “dimmer switch” than an all-or-nothing approach to combating the virus.

“We use every piece of reliable medical information we can to make decisions,” Scrase said Wednesday.

The goal, he said, is to keep as much of the economy going as possible while limiting the number of deaths.

‘Major flaws’

Carol Wight, CEO of the New Mexico Restaurant Association, said the new study “has major flaws.”

The research, she said, failed to take into account the safe practices now employed at restaurants throughout the country and in New Mexico — including the use of face masks, changes to seating layouts, social distancing and disinfection of surfaces. It also didn’t distinguish between the risks of indoor vs. outdoor restaurant settings, Wight said.

“Due to the complexities of the real world, predictive models are inherently fraught with error even under the best of circumstances,” the National Restaurant Association said in a written statement shared by Wight. “In this case, the researchers’ model seems to fit their data, so they conclude that it is reasonably accurate. However, this is not enough to assert that restaurants are a significant source of risk across the entire United States.”

Gov. Michelle Lujan Grisham, a Democrat, has faced fierce criticism from Republican lawmakers who have pushed to more quickly reopen the economy. Too many small, local businesses, they say, simply cannot survive the restrictions.

Cellphone tracking

The research published in Nature was led by experts at Stanford and Northwestern universities, Microsoft and Biohub, a medical research center in the San Francisco area.

They analyzed anonymous cellphone data tracking the movements of 98 million people throughout the country earlier this year and built a statistical model to simulate the spread of COVID-19 in 10 large metropolitan areas. They examined a host of reopening strategies to study which would be most effective.

The research flagged full-service restaurants, fitness centers, snack bars and cafes, and hotels and motels as the top four riskiest nonresidential locations. Restaurants were by far the most likely to drive infections — likely because they are more densely populated and people tend to stay there a long time, according to the paper.

“Our model predicts that a small minority of ‘superspreader’ (points of interest) account for a large majority of infections and that restricting maximum occupancy at each POI is more effective than uniformly reducing mobility,” the authors wrote.

In Chicago, for example, about 10% of the points of interest accounted for 85% of the predicted infections.

“If a minority of POIs produce the majority of infections,” the authors said, “then reopening strategies that specifically target high-risk POIs should be especially effective.”

New Mexico’s anti-virus strategy has been both targeted and broad. The new public health order restricts occupancy at businesses and other specific places, while also instructing people to stay home in general.

An earlier version of the order allowed indoor dining at restaurants and breweries at 25% of capacity.

The existing order, like the one before it, also requires the closure of businesses that have repeated COVID-19 infections in the workplace.

“It’s a very infectious virus,” Scrase said. “We know that it just spreads like crazy.”

‘Shopping’ tops list

The analysis in Nature examined data that included stationary points of interest, tracking’s people’s movement to nonresidential locations. It didn’t mention attendance at events that occur periodically or change locations, such as an outdoor protest or festival.

The study didn’t examine schools or child care centers because of limits on data for children under 13. Bars, parks and hospitals also weren’t analyzed because of data limits.

In New Mexico, reports released by the state Department of Health don’t precisely point to where residents are being exposed to the virus.

But for people with the disease who have had their cases investigated, “shopping” is the most common activity they report having participated in before infection — a category that includes trips to the grocery store, for example. Visits to a restaurant or brewery or attendance at a gathering are the other most frequently reported activities.

Demographics

The research in Nature examined why COVID-19 hits some demographic groups harder than others. The authors said people in low-income communities tend to reduce their mobility less — perhaps because they don’t often have the option of working from home — and the places they visit are more crowded.

The finding has implications for New Mexico, one of the poorest states in the nation.

New Mexico hasn’t released income data on COVID-19 victims, but older adults and Native Americans make up a disproportionate share of those who have died, according to the state’s mortality reports.

Native Americans, for example, account for 41% of the state’s coronavirus-related deaths, although they are just 11% of the state population.