This change comes about as the understanding of pre-symptomatic and asymptomatic infected people with the virus can spread the virus and this spread can come through simple speech. From a study out of UC Davis, "Normal speech by individuals who are asymptomatic but infected with coronavirus may produce enough aerosolized particles to transmit the infection.."
State governments such as Pennsylvania also recommend that people wear face coverings when in public venues.
This is not a contradiction, or a flip flop, but rather an understanding of how the situation has changed with a growing number of cases in the US. As more become infected, this increases the likelihood of asymptomatic or pre-symptomatic people in settings where they can spread the virus through aerosolization. By wearing a face covering, it reduces the risk that the wearer will spew out significant aerosols.
These are the cloth or homemade masks, not the surgical or N-95 masks which should be reserved for those working in the medical field or other high risk operations.
FDA COVID-19 FAQs
https://www.fda.gov/food/food-safety-during-emergencies/food-safety-and-coronavirus-disease-2019-covid-19
Should employees in retail food and food production settings wear face coverings to prevent exposure to COVID-19? (Posted April 4, 2020)
On April 3, the CDC released an updated recommendation regarding the use of cloth face coverings to help slow the spread of COVID-19. CDC recommends the use of simple cloth face coverings as a voluntary public health measure in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies).
For workers on farms, and in food production, processing, and retail settings who do not typically wear masks as part of their jobs, consider the following if you choose to use a cloth face covering to slow the spread of COVID-19:
- Maintain face coverings in accordance with parameters in FDA’s Model Food Code sections 4-801.11 Clean Linens and 4.802.11 Specifications.
- Launder reusable face coverings before each daily use.
- CDC also has additional information on the use of face coverings, including washing instructions and information on how to make homemade face covers.
NOTE: The cloth face coverings recommended by CDC are not surgical masks or N-95 respirators. Those are critical supplies that must continue to be reserved for healthcare workers and other medical first responders, as recommended by current CDC guidance.
CDC New Release
https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover.html
Recommendation Regarding the Use of Cloth Face Coverings, Especially in Areas of Significant Community-Based Transmission