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  • [♪ INTRO]

  • This episode was filmed on April 7th, 2020.

  • If we have a more recent episode about COVID-19,

  • we will include it in the description.

  • On April 3rd, the U.S. Centers for Disease Control and Prevention

  • started recommending that people wear a mask over their face

  • when they go out in public.

  • These guidelines don't replace social distancing

  • it is still really important to stay away from other people

  • as much as possible right now.

  • Which I am doing by filming this at my home.

  • But masks are designed to keep the virus from spreading

  • in more crowded places that we still need to go to,

  • like grocery stores.

  • Except, for many of us, this isn't the message we've gotten

  • for the last couple of months.

  • Before this, many health organizations recommended not wearing a mask

  • unless you are sick or caring for someone who is.

  • So... what changed?

  • Well, it's not that scientists learned something new about masks.

  • It's that they uncovered more about how the virus

  • seems to be spreading.

  • In most cases, a mask won't keep you from getting sick

  • if there are viruses in the air around you.

  • We've talked about this before, but when you breathe

  • while wearing a basic mask, a lot of the air you inhale

  • comes in from around the mask's edges.

  • And since that air doesn't pass through the mask,

  • the virus gets carried in along with it.

  • Respirators and more sophisticated devices can offer

  • better protection if they're fitted and used properly,

  • butand I'm sure you've heard thisthose should be saved

  • for healthcare workers, who are getting up close and personal

  • with COVID-19 patients on a regular basis.

  • Still, while basic masks can't really keep viruses

  • from getting in, they are much better at keeping them

  • from getting out.

  • See, when you cough or sneeze, or even talk, it's not just air

  • that comes out, but little particles of moisture

  • that scientists call respiratory droplets.

  • And if you're sick, those droplets can be teeming with viruses.

  • But a mask traps many of those droplets inside.

  • That's why the CDC and World Health Organization have recommended

  • for months that anyone who's coughing, sneezing, or sick wear a mask.

  • But now, things are changingat least, for the CDC.

  • And that's because new research suggests it's not just people

  • who know they're sick that can infect others.

  • We now know that some cases of COVID-19 can be pretty mild.

  • And while most people with a mild case develop a fever,

  • it's possible they might not know they're sick.

  • But beyond that, there seem to be cases where people with the virus

  • never show symptoms at all but can still transmit it.

  • And for the rest, evidence is mounting that it's possible

  • to spread the virus when you're presymptomatic

  • in other words, before you start showing symptoms.

  • For instance, a study published on April 1st found that around 6%

  • of cases in Singapore could be linked to a person

  • who was presymptomatic.

  • And in Chinese cases outside the epicenter of Hubei province,

  • the figure was more like 13%.

  • By definition, people who are presymptomatic aren't yet coughing

  • or sneezingand may not be for several days.

  • But even normal activities like talking, or ones you can't avoid,

  • like breathing, can create respiratory droplets.

  • And while we currently don't have evidence that those particles

  • are big enough to transmit the virus, some scientists

  • and a few preliminary studiessuggest it is a possibility.

  • In any case, asymptomatic and presymptomatic transmission does seem

  • to be happening.

  • And that's why the official guidance in the U.S. and elsewhere

  • is shifting to recommend we all start wearing masks.

  • Because it is possible for someone to be transmitting COVID-19

  • without even knowing they are sick.

  • So, by wearing a mask, we are helping protect everyone else.

  • In response to this, you've probably seen people make their own masks,

  • using things like scrap fabric or bandanas.

  • And although that might seem like a kind of trivial precaution, the limited evidence we

  • have suggests they do seem to be helpful.

  • Like, look at one study that came out in 2013.

  • Because it was done seven years ago, it wasn't on the COVID-19 virus,

  • but it did find that a cotton T-shirt blocked about half of the viruses

  • in a cough, while a tea towel stopped 72%.

  • Of course, at this point, there is a lot that we don't know

  • about this coronavirus, and there haven't been many studies

  • about homemade masks.

  • That's why some experts disagree with the new CDC recommendations.

  • But other researchers think that doing something

  • is better than nothing.

  • If you want to make a mask, the CDC website has several patterns,

  • including ones that don't require any sewing,

  • and we'll include a link to that in the description.

  • But there is an important thing to know here:

  • Even though just wearing a mask can feel kind of reassuring,

  • for them to work, you have to use them right.

  • I happen to have a mask right here, so I can do a demo for you.

  • You should wear them tight over your nose and mouth

  • and avoid touching the sides and straps as much as possible.

  • And you shouldn't touch the front of the mask at all.

  • It sounds silly, but you should basically treat it

  • like it's covered in raw chicken or poop.

  • So, when it's time to remove your mask, do it using

  • the straps or strings.

  • Then, after every use, store your mask in a bag until you can

  • wash it in a washing machine or with soap and hot water.

  • And of course, wash your hands before and after touching the mask.

  • As our understanding of COVID-19 continues to improve,

  • there's a good chance these guidelines could change again.

  • But, look - that's honestly a good thing.

  • Guidelines change when we understand more about this virus

  • and this disease.

  • And that continues to happen.

  • At the end of the day, this is going to be information

  • that helps us keep each other safe and figure out

  • how to get through this.

  • Thanks for watching this episode of SciShow!

  • We hope you're staying safe and well out there.

  • If you're at home with the kids these days,

  • I wanted to recommend SciShow Kids!

  • That's our channel that is designed for young elementary schoolers.

  • My son loves it!

  • We are watching a lot of it right now.

  • We have more than 300 episodes over there right now,

  • and we hope they'll be helpful to you.

  • You can find them at youtube.com/scishowkids.

  • [♪ OUTRO]

[♪ INTRO]

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