12 h, jan 30, 2020 y - CDC: "does not currently recommend the use of face masks for the general public."

Description:

https://www.cdc.gov/media/releases/2020/t0130-novel-coronavirus-update-telebriefing.html
https://web.archive.org/web/20200131010304/https://www.cdc.gov/coronavirus/2019-nCoV/summary.html
https://web.archive.org/web/20200131023610/https://www.cdc.gov/coronavirus/2019-ncov/about/prevention-treatment.html