Why was the American public told not to wear face masks?

From Taiwan: Taipei, April 3 (CNA) All users of public transport will need to wear facial masks or risk a maximum fine of NT$15,000 (US$496), effective as of Friday, a top official from the Central Epidemic Command Center (CECC) said, as parts of efforts to prevent the spread of the COVID-19 coronavirus.

“If we spot someone not wearing a mask, we will ask them to put one on and if they refuse to do so, we will fine them in accordance to the Communicable Disease Control Act,” Chen said.

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The reason for enforcing users of public transport to wear masks is because proper social distancing cannot be properly implemented in such situations, Chen Shih-chung said.