NEW YORK (NYTIMES) - Restaurants, gyms, cafes and other crowded indoor venues accounted for some eight in 10 new infections in the early months of the United States coronavirus epidemic, according to a new analysis that could help officials around the world now considering curfews, partial lockdowns and other measures in response to renewed outbreaks.
The study, which used mobile phone mobility data from 10 US cities from March to May, also provides an explanation for why many low-income neighbourhoods were hardest hit. The public venues in those communities were more crowded than in more affluent ones, and residents were more mobile on average, likely because of work demands, the authors said in the research published in the journal Nature on Tuesday (Nov 10).
The data came from the metro areas of Atlanta, Chicago, Dallas, Houston, Los Angeles, Miami, New York, Philadelphia, San Francisco and Washington, DC.
Infectious disease models had provided similar estimates of the risk posed by crowded indoor spaces, going back to February; all such models are subject to uncertainties, due largely to unforeseen changes in community behaviour.
The new analysis provides more precise estimates for how much each kind of venue contributed to urban outbreaks, by tracking hourly movements and taking into account the reductions in mobility from lockdown restrictions or other changes that occurred during those first crucial months. It did not model infection in schools or office workplaces.
"Restaurants were by far the riskiest places, about four times riskier than gyms and coffee shops, followed by hotels" in terms of new infections, said computer scientist Jure Leskovec from Stanford University and senior author of the new report, in a conference call with reporters.
The study was a collaboration among scientists at Stanford, Northwestern University, Microsoft Research and the Chan Zuckerberg Biohub.
Public officials across Europe and in parts of the United States, including Governor Phil Murphy of New Jersey, have begun to institute partial closures of restaurants and bars, or limited indoor hours, as new infections have surged in recent weeks.
In New York City, a spike in virus cases threatens the city's recovery and could mean "a lot more restrictions", Mayor Bill de Blasio said on Monday.