Updated at 8:35 p.m. ET

President Trump said Friday the Centers for Disease Control and Prevention now recommends that people wear cloth or fabric face coverings, which can be made at home, when entering public spaces such as grocery stores and public transit stations. It is mainly to prevent those people who have the virus — and might not know it — from spreading the infection to others.

The guidelines do not give many details about coverings beyond: "cloth face coverings fashioned from household items or made at home from common materials at low cost can be used as an additional, voluntary public health measure."

Trump emphasized that wearing masks in public is voluntary and said he will not be doing so.

A federal official tells NPR that the White House pressured the agency to limit the scope of the wording of the new guidance. The CDC wanted to emphasize that the recommendation could be helpful for Americans in all parts of the country, given that it is becoming increasing difficult to designate particular areas as "hot spots," since the virus is present in so many areas of the country. In the end, this source tells NPR, the White House insisted the guidance emphasize the use of face coverings in areas where there is widespread community transmission of the virus.

U.S. health authorities had discouraged healthy Americans from wearing facial coverings for weeks, saying they were likely to do more harm than good in the fight against the coronavirus — but now, as researchers have learned more about how the highly contagious virus spreads, officials have changed their recommendations.

U.S. health authorities have long maintained that face masks should be reserved only for medical professionals and patients suffering from COVID-19, the deadly disease caused by the coronavirus. The CDC had based this recommendation on the fact that such coverings offer little protection for wearers, and the need to conserve the country's alarmingly sparse supplies of personal protective equipment.

Still, as the virus spread to every state in the U.S., it has become clear that people can contract and spread the virus without showing symptoms, rendering it difficult — if not impossible — to distinguish healthy from infected individuals without a formal test. So, it may protect other people who come into contact with the unknowing individual.

And the mask need not be professional-grade to offer some benefit. In fact, officials say it probably shouldn't be: The CDC recommends constructing your own cloth mask, so as to help ensure that doctors and nurses can obtain access to medical-grade surgical or N95 masks amid a widespread shortage of supplies.

With this announcement, the U.S. is following the lead of a number of other countries that have been urging — or outright ordering — their residents to don masks in public. The expanding list includes China and South Korea, where officials have even taken the step of distributing masks.

And while the European Centre for Disease Prevention and Control continues to discourage the use of face masks, some European countries, such as Austria and the Czech Republic, have told their residents to cover up their mouths and noses before entering a store.

This week, the mayors of Los Angeles and New York City also urged residents to do the same.

