And perhaps it would have, had it not been for the masks.
In the days after, health officials contact-traced all 139 people exposed to the stylists and asked them to self-quarantine for two weeks. None reported feeling sick during the 14 days that followed their salon appointments. The researchers also offered the clients free diagnostic tests for the coronavirus. Sixty-seven of them accepted; the rest declined. Of those tested, all turned up negative.
“I was shocked,” Ms. Findley said.
Follow-up interviews with 104 of the clients revealed that, in accordance with guidelines, patrons and stylists alike had worn masks for the duration of almost all the encounters documented by the study.
A small handful of clients had donned N95 respirators — devices designed to filter out 95 percent of airborne particles and one of the best forms of protection for health workers. Since the start of the pandemic, N95s have been in dire short supply.
But a majority of people in the study, including the two stylists, opted for cloth coverings or surgical masks — loosefitting accessories that don’t form an airtight seal around the face.
These products are imperfect. But several studies, including some initiated long before the pandemic’s start, have pointed to their usefulness in stymieing the spread of viruses from the wearer’s airway, Julian Tang, a virologist at the University of Leicester who wasn’t involved in the study, said in an email. To a lesser extent, they may also protect a user from incoming spray.
In this case, even homemade masks that can’t reliably snuff out every virus-laden particle seemed to do the trick — an incredibly encouraging finding, Dr. Gutiérrez said. “Had they not been using those masks, we would have expected a totally different situation,” he said.
Of course, masks alone can’t be considered a foolproof “safety net,” said Saskia Popescu, a hospital epidemiologist and infectious disease expert in Arizona who wasn’t involved in the study. “This is not an excuse to let you go about and do whatever you want, especially if you’re symptomatic.”