Science Magazine interview with George Gao, director-general of the Chinese Center for Disease Control and Prevention (CDC):[1] "Q: What mistakes are other countries making? A: The big mistake in the U.S. and Europe, in my opinion, is that people aren't wearing masks. This virus is transmitted by droplets and close contact. Droplets play a very important role—you've got to wear a mask, because when you speak, there are always droplets coming out of your mouth. Many people have asymptomatic or

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... esymptomatic infections. If they are wearing face masks, it can prevent droplets that carry the virus from escaping and infecting others." China and Hong Kong have specific universal mask recommendations for the general population, mostly concerning those in crowded places or at increased risk. Early in the pandemic in the US, there was a bright line claim that seemed suspicious to me: masks that are not N95 offer no protection. Another follow up claim: masks are only to prevent the spread by the wearer and do not protect the wearer. Neither claim is exactly proven and the veracity with which they were spoken may have undermined protection. The absence of incontrovertible scientific studies supporting widespread mask use is not the same as evidence that masks are ineffective. There is not evidence that masks worn by the general public are ineffective. However, many US scientists have made that very claim. Healthcare professionals who publicly said masks are ineffective or not recommended include: Jerome Adams, US Surgeon General; the US CDC; David Heymann, epidemiologist with WHO at the time of SARS (because of fear of improper use); Emily Landon, University of Chicago Medical School (because of improper use and because N95 are the only masks prove effective)[2]; Hyo-Jick Choi, Chemical Engineer, University of Alberta (because masks are for large droplets only); Eric Toner, Johns Hopkins ("no harm in it but it is not likely to be very effective") [3]; Alax Azar, HHS secretary, (masks should be just for healthcare workers); [...]