Asymptomatic spread was confirmed as significant the end of Feb when they tested the cruise passengers, and most of Asia already had some form of mandatory mask

Asymptomatic spread was confirmed as significant the end of Feb when they tested the cruise passengers, and most of Asia already had some form of mandatory mask order in place. Widespread mask usage was shown in at least a few NIH studies to reduce transmission, though most looked at getting a virus versus transmitting it IIRC. To me it looks like CDC/WHO hubris caused them to completely disregard Asia's approach until they could "discover" it themselves.