“As the C.D.C. continues to study the spread of the Covid-19, they’re recommending people wear cloth face coverings in public settings where social distancing measures can be difficult to maintain,” Mrs. Trump said in an accompanying video, referring to the Centers for Disease Control and Prevention. She cited grocery stores and pharmacies as examples.

“Remember,” she added, “this does not replace the importance of social distancing.”

After a slow start to acknowledge the virus, Mrs. Trump has since issued a string of public service videos meant to echo public health guidelines on social distancing and hand washing.