While Americans continue to debate whether face masks can stop the spread of coronavirus, a new report offers compelling evidence that the coverings do indeed work. In May, two hairstylists at a Missouri salon who had COVID-19 but wore face masks cut the hair of 139 masked customers for roughly a week, and did not infect a single client. They also did not infect any of the clients' contacts or any of the other stylists in the salon, researchers report. The first stylist worked with clients for eight days while symptomatic, while the second stylist did the same for five days, the researchers wrote. "The message is clear: Face masks work," said Dr. Robert Glatter, an emergency room physician at Lenox Hill Hospital in New York City.