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  • This is a video made by a group of German physicists.

  • The circle in the background is a kind of mirror,

  • that, combined with a special photography technique,

  • allows you to see the flow of air.

  • In this case, it is showing how far air particles travel when someone breathes.

  • And when they coughwhich makes the respiratory particles travel further, and faster.

  • This is what it looks like when someone coughs into their hand.

  • And into their elbow.

  • And this shows the travel of air particles when coughing while wearing two types of masks:

  • a dust mask, and a surgical mask.

  • This isn't a scientific study. It simply shows something face masks do very well:

  • They limit how far away from you respiratory particles can travel.

  • But whether you've been told to wear a face mask to prevent the spread of Covid-19,

  • probably depends on where you live.

  • In some East Asian countries, it's already common practice.

  • Some European countries have also started mandating face masks in public spaces.

  • But in the US, the message from the federal government has been inconsistent.

  • There's no reason to be walking around with a mask...

  • it's not providing the perfect protection that people think that it is.”

  • The CDC recommends wearing cloth face coverings in public settings

  • where other social distancing measures are difficult to maintain."

  • This is voluntary. I don't think I'm going to be doing it.”

  • Unless you live somewhere that mandates it, whether you wear a face mask is probably up to you.

  • But making that decision for yourself is a lot easier

  • if you understand what face masks can actually do.

  • And what they can't.

  • Here's where the experts agree: If you are sick, and you leave the house,

  • you should wear a face mask, because it keeps your germs in.

  • Most of the uncertainty around masks is related to a separate question:

  • whether healthy people should wear them too.

  • Right away, though, that distinction, between sick with covid-19, and healthy,

  • is more complicated than it sounds.

  • People who catch covid-19 don't feel symptoms for 5-6 days on average,

  • and even up to 14 days,

  • but are contagious before that.

  • And based on what we know right now, about 25% of people who catch it never show symptoms at all,

  • but are also contagious.

  • In other words, especially with covid-19,

  • feeling healthy doesn't necessarily mean you don't have it.

  • "I think we should all be acting, and also all assume, that we're infected."

  • Shan Soe-Lin is an expert on global public health,

  • and Robert Hecht is a professor of clinical epidemiology.

  • And they say the possibility of being asymptomatic is one of the best cases for universal mask wearing.

  • "Those who are actually infected and don't know it, or showing almost no symptoms,

  • it's not even primarily for their own health.

  • It's for the health of their family and neighbors."

  • But let's say you definitely, 100%, do not have the virus.

  • The first thing you need to know is that no mask can actually guarantee that you won't get it.

  • Instead, the best way to think about face masks is as part of a larger set of protective measures,

  • along with social distancing and hand-washing.

  • Used together, they don't protect you completely,

  • but they dramatically lower your odds of infection.

  • "I think of it as a protective triad, with the virus trying to get in.

  • And if you don't have one of the branches in it,

  • then you're not protecting the whole thing.

  • And if you didn't have a mask, could you do better with social distancing and hand-washing? Sure.

  • But having all three is really, really important."

  • To understand how that works, let's look at the two ways covid-19 is transmitted.

  • One way is by touching an infected surface and then touching your face.

  • This is called fomite transmission.

  • And frequent hand-washing is the best defense against this.

  • But wearing face masks correctly can play a role too:

  • "Masks do a really good job of keeping you from touching your face."

  • The second way someone's respiratory particles can reach you is directly. Like this:

  • This is a slowed-down recording of a sneeze.

  • It shows the kinds of respiratory particles a sneeze emits,

  • and how far they travel.

  • From a sick person, these droplets are packed with millions of viral particles

  • that fall in close range, and infect whatever they land on.

  • Social distancing protects us from droplets, by keeping you away from the particles emitted

  • through sneezing, coughing, or even talking.

  • But face masks could help there, too:

  • "If someone sneezes a couple of feet away from you, it'll protect some of the bigger splashes."

  • That also means face masks are especially important

  • for people who don't have the privilege of being able to social distance:

  • "That would be cops. That would be grocery clerks."

  • "Taxis, Uber, FedEx, UPS..."

  • "Anyone who's coming into contact with a lot of people,

  • and maybe can't always maintain that six-foot distance."

  • Look at this video again, though,

  • and you'll see that we also produce these longer-range, smaller particles,

  • which evaporate, and can leave the virus hanging in the air.

  • These are called aerosols.

  • And we still don't really know how infectious they are for the average person.

  • But experts think they mostly pose a threat to medical workers,

  • who work up close to patients with Covid-19.

  • "If you're a foot away from the patient, who's coughing as you're trying to intubate them,

  • aerosols are going everywhere.

  • For you and me, just walking around, walking your dog, going to a grocery store,

  • your risk is way higher from fomites."

  • A common mask that protects against aerosols is called an N95 respirator.

  • Its name comes from its material's ability to filter out 95% of aerosol particles.

  • It's also fitted to form a seal around your mouth and nose, so there's no leakage.

  • In lots of places, N95s are in short supply, because of diminished government stockpiles

  • and disruptions in the supply chains.

  • And that's true for all disposable masks, not just N95s.

  • That's why the US Center for Disease Control says that unless you're a health care worker,

  • you shouldn't be using either N95s or regular surgical masks.

  • They're needed in hospitals, and the level of protection most people need can come from

  • a simple cloth mask.

  • The CDC recommends any kind of tightly woven cotton for the mask, or even a T-shirt.

  • You can make them by consulting the countless internet tutorials out there,

  • or buy them from the many vendors who manufacture them.

  • But they only work if you wear them correctly.

  • "So what kind of masks are you wearing? Do you have them handy? Could you show us?"

  • "We thought you might ask."

  • "This is all it takes to put it on:

  • Just grab it by the loops. Keep your hands off the central part.

  • Put it over your nose and mouth. Loop it around the ears.

  • Be careful not to touch it when you're outside. Keep your hands away from your face.

  • When you come back in, after walking the dog,

  • or doing the groceries, do the same thing in reverse.

  • Put it off to the side. Don't start playing with it.

  • And then at the end of the day, pop it in the washer."

  • "You wash it every day?"

  • "I wash them every night. And, you know, if you don't have a washer,

  • you can hand wash them every night. They're very small and they'll be dry by the next morning.

  • So if people can have a couple, it would be better.

  • But if you only have one, then just wash it at night."

  • Face masks highlight something important in the fight against covid-19:

  • That it isn't always about protecting yourself.

  • It's about protecting the people around you.

  • And if everyone is doing it, we all protect each other.

  • "There's a visual messaging that comes from wearing a mask:

  • A reminder to everybody, that we're not in normal times now.

  • Everyone needs to be doing everything they can to protect themselves, and other people."

This is a video made by a group of German physicists.

Subtitles and keywords

B1 INT US mask face covid 19 covid respiratory wearing

What face masks actually do against coronavirus

Video vocabulary

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