A hay bale along the edge of a cattle pasture near Florence, Kan., is adorned with a face and surgical mask, Sunday, April 5, 2020, amid the ongoing coronavirus pandemic. Credit: Travis Heying | AP

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The Centers for Disease Control and Prevention last week began recommending that Americans wear cloth face masks when they leave the house, particularly if they are in areas with high rates of community transmission. Face coverings are especially important in areas where social distancing may be difficult, such as grocery stores and pharmacies.

This is a reversal of previous guidance that said masks weren’t really helpful.

[Our COVID-19 tracker contains the most recent information on Maine cases by county]

The change came because it has become increasingly clear that people without any symptoms — known as asymptomatic or pre-symptomatic — are transmitting coronavirus to others. Some of those people do become very sick, even if those who transmitted the virus to them did not.

Wearing a mask can help reduce this spread.

President Donald Trump announced the recommendation on Friday, but immediately muddled the message, saying he wouldn’t follow the new guidance. As with much else he has said during the coronavirus pandemic that is killing hundreds of Americans per day, you should listen to the medical experts, not the president.

In light of recent studies about coronavirus transmission, the president said, “the CDC is advising the use of non-medical cloth face covering as an additional voluntary public health measure.”

“So, it’s voluntary. You don’t have to do it,” he went on. “They suggest it for a period of time. But this is voluntary. I don’t think I’m going to be doing it.”

True, it is voluntary, but there are solid health reasons that you should do it.

Wearing a mask does more to protect others than it does to protect you. Essentially, you should wear a mask in case you are carrying the coronavirus and don’t know it yet.

As Dr. Dora Mills, senior vice president for community health at MaineHealth, explained to BDN subscribers last week, coronavirus is spread through respiratory droplets, which come out of your nose and mouth as you cough, sneeze and even talk. A cloth mask can trap these droplets, before they are sprayed on surfaces, your hands and even other people.

“If you’re in that pre-symtomatic phase, a cloth mask can prevent you from transmitting it to somebody else,” she said.

She did caution that wearing a mask makes some people touch their face and eyes more than they normally would, which can also transmit the virus. So, be mindful of this and keep your hands away from your face.

And, Mills stressed, if you have medical-grade masks, you should preferably donate those types of masks to your local hospital, where masks and other personal protective equipment are in short supply, rather than wearing them yourself.

You don’t need to buy a fancy mask, although many companies and people are now selling them. You can sew one yourself. Or even easier, the surgeon general offers a short video showing how to make a mask by simply folding cloth and using hair elastic or even rubber bands to secure it to your face.

Make sure to wash your mask regularly.

“Americans have repeatedly stepped up to make contributions to our war on the coronavirus in exceptional ways,” Health and Human Services Secretary Alex Azar said in a statement on Friday. “Face coverings are a new, voluntary opportunity for a unified national effort: I’m wearing one to protect you, and you’re wearing one to protect me. Taking this step will protect our loved ones, our communities, and our country from the invisible enemy we’re fighting together.”

I’m wearing one to protect you, you’re wearing one to protect me. That is the perfect way to sum up this new effort to slow the spread of coronavirus.

Watch: Nirav Shah on whether you should use fabric masks