Should I wear a face mask to help slow the spread of COVID-19?

Rather than using a medical grade mask, you should wear a homemade or fabric mask when out and near other people (in addition to social distancing, washing your hands, and avoiding touching your face).

Even the U.S. President states, "I would say do it. But use a scarf if you want rather than going out and getting a mask. … It doesn’t have to be a mask." And he's not wrong.

Wearing a mask or scarf helps protect you, and also helps protect others from being infected by you, even if you have no symptoms.

How do I make my own face mask?

For more homemade mask guides click here.

If you don't want to make one, you can use something like a scarf, bandana, balaclava, or neck warmer/snood -- just make sure to tightly cover your mouth and nose (and wear glasses to protect your eyes).

Do I need an N95 mask?

No. Unless you are a healthcare worker or working around a lot of people, you probably don't need an N95 mask.

There is a shortage of N95 masks, so leave them to those who need them and donate them if you have any.

According to this study, a homemade mask can be made out of a cotton blend t-shirt or tea towel and still be ~70% effective at filtering a virus from the air in droplets:
While a homemade mask isn't perfect, they conclude that it "would be better than no protection." Face masks help by catching respiratory droplets that could carry the virus. So make sure to wash your hands if you touch the outside of your mask and sanitize it often.

Is a mask that is 70% effective going to do anything?

Time for some back of the envelope calculations. Let's use Alice & Bob as examples:
1) Alice doesn't have the virus. If she wears a 70% effective mask, she has a 30% chance of getting it.
2) Bob does have the virus. If he wears a 70% effective mask, it can help prevent him from coughing or sneezing droplets into Alice's face, he has a 30% chance of spreading it.

So Alice has a 30% chance of getting it and Bob has a 30% of spreading it, leading to a 9% chance of transmission (.3 * .3 = .09). All things being equal, the virus is 91% less likely to spread from Bob to Alice if they both wear masks than if neither of them wear masks.

The more people who wear masks, the better for everyone.

According to this study, "If 50% of the population were to wear masks, only 50% of the population would be infected by the virus. Once 80% of the population wears a mask, the outbreak can be stopped immediately."

Why do I need to wear a mask?

According to this study, the virus that causes COVID-19 (SARS-CoV-2), can live in the air for at least 3 hours:
While it may not meet the technical definition of being "airborne", SARS-CoV-2 can be spread through the air between people via droplets -- see this Wired article "They Say Coronavirus Isn't Airborne—but It's Definitely Borne By Air".

Here's a video from this study showing the airflow between two people talking:


Even if you aren't coughing or sneezing, droplets can be transmitted when you talk or even breathe. And a recent study shows that droplets can travel up to 27 feet. Wearing a mask can help protect you, and it can help protect everyone around you, ultimately helping to flatten the curve and slow the spread of COVID-19.

But what if I don’t have symptoms, should I still wear a mask?

YES, absolutely! Studies have shown that you can be contagious even if you don't have symptoms. Up to 25% of people infected with the coronavirus may be asymptomatic. This is probably a big reason why COVID-19 is spreading so quickly -- so many people are going about their business, thinking they are fine because they don’t have symptoms, but in actuality, they could be spreading it!

Because of asymptomatic transmission, everyone should act as if they have the virus, which means, wear a mask!

But what about six feet of social distancing? Isn’t that enough?

Let’s be realistic. Even if you are at home sheltering in place, you will likely inevitably get closer than six feet to someone else. At the grocery store? Picking up your takeout? Walking down the sidewalk and crossing paths with someone? On a bus, or subway, or in a taxi? Bump into a friend while jogging and forget about the 6 feet rule?

Or maybe you are still working because your job is considered an essential service.

Consider Viral Load:

Some studies also show that the severity of COVID-19 is a function of how much of the virus you were exposed to (called the "viral load"). Wearing a mask can help reduce your viral load, so even if you do get exposed to the virus, hopefully it will be less severe than if you weren’t wearing a mask. According to a recent study, the jury is still out on this one, but either way, it still makes sense to wear a mask.

Other benefits of wearing a mask:

1) If everyone defaults to wearing a mask, it can destigmatize it. If very few people wear a mask, some people might be reluctant to wear one because they are worried that people will think they are sick.
2) When you are wearing a mask, you are less likely to touch your face.

What do the experts say about wearing face masks to slow the spread of COVID-19?

"If you mandated that the entire population had to wear a mask when they went out, all those asymptomatic carriers that are now transmitting it through respiratory droplets -- it would be much harder for them to transmit it."
- Dr. Scott Gottlieb, Former FDA Commissioner in The Wall Street Journal

"It’s really a perfectly good public health intervention that’s not used. It’s not to protect yourself. It’s to protect people against the droplets coming out of your respiratory tract."
- KK Cheng, Director, Institute of Applied Health Research, University of Birmingham in Science

"Masks that are effective at 'flattening the curve' can be made at home with nothing more than a T-shirt and a pair of scissors. We should all start wearing these simple, homemade masks whenever we’re in out in public."
- Jeremy P. Howard, Faculty at University of San Francisco in The Washington Post and Founder of masks4all.co

What can I do to help?

• Consider donating any unused N95 masks or even money to these organizations.
• Help spread the word and convince your friends and family to wear a homemade face mask when they go out.
• Reach out to your state & local governments and demand interventions like masks and social distancing. Point them to covidactnow.org for models and show them how the Mayor of Los Angeles requests citizens wear masks in public.
• Use the tag #masks4all on social media.
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• Make sure to continue practicing other CDC guidance including social distancing, washing your hands frequently, and avoiding touching your face in addition to wearing a homemade or nonmedical fabric mask if you are out and near other people.

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1. Scientific Literature Supporting Wearing of Face Masks (27 March 2020)
2. How to Make a Face Mask at Home (27 March 2020)
3. How to Donate Face Masks to Healthcare Providers (27 March 2020)