For weeks, Americans were told that the general public does not need to wear masks while in the public.
Then on Friday, President Donald Trump announced that the CDC would issue guidance that face coverings not intended to be used for medical purposes should be used on a voluntary basis while in the public.
Why the change in guidance?
On Wednesday, the The National Academies of Science, Engineering and Medicine released findings that indicated that COVID-19 is spread more easily than previously thought. While past research indicated that those with mild symptoms could spread the virus through a cough or sneeze, the National Academies said that germs could spread simply by talking or breathing by those who are asymptomatic or who are pre-symptomatic.
The research is preliminary, and requires further study, but the National Academies' findings prompted a change in the CDC's guidance.
"Currently available research supports the possibility that SARS-CoV-2 could be spread via bioaerosols generated directly by patients' exhalation," the research said. "One must be cautious in imputing the findings with one respiratory virus to another respiratory virus, as each virus may have its own effective infectious inoculate and distinct aerosolization characteristics."
The National Academies said that personal collectors worn by samplers also were positive even though patients were not coughing while samplers were present.
The CDC's guidance stressed several points: That wearing a face covering is not a substitute for social distancing, and that the public should not use medical or surgical masks. The recommendations suggest the public should use fabric or cloth that covers the mouth and nose.
"The virus can spread between people interacting in close proximity—for example, speaking, coughing, or sneezing—even if those people are not exhibiting symptoms. In light of this new evidence, CDC recommends wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies) especially in areas of significant community-based transmission," the CDC said.