See here: "In Hong Kong, there was never any doubt about the need for face masks. Most people here, including an epidemiologist helping guide the response, are adamant that widespread mask use has been crucial in keeping the city from becoming a viral hot zone. “If not for universal masking once we depart from our home every day, plus hand hygiene, Hong Kong would be like Italy long ago,” said K.Y. Yuen, a Hong Kong microbiologist advising the government. “If you look at where we’ve had clusters, it’s places where the masks come off, like hot-pot family dinners or Buddhist temples." Which...