Can Face Masks Prevent Corona Virus Infections?

Liz showing her self-made facemask

The use of facemasks by the general population is generally discourages in the US and Europe, often stating "they do not help", and claiming scientific evidence. In stark contrast, the widespread use of facemasks has been part of the measures in all Asian countries and regions that have contained the infection, including Taiwan, Honk Kong, South Korea, and Japan. This post analyses some of the relevant science and health agency recommendations.

In the US, both the director of the CDC and the Surgeon General advised against using facemasks. A look at the "How To Protect Yourself" page at the CDC website states that "if you are not sick, you do not need to wear a facemask":

From https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html,
Captured 3/29/2020. Highlighting added for this post.

However, the highlighted region explains why this advice is given: facemasks are in short supply. To a large extend, this was caused by offshoring production - 95% of surgical masks and 70% of N95 respirators are made overseas.

Prima facie evidence indicates that facemasks work to prevent infections: health care personnel generally has to wear facemasks around infective patients, and the (cheaper) surgical masks derive their name from the fact that they are worn in surgeries, primarily to prevent infection of the patient. But let's look a the science.

There are some studies that show that facemasks used by the general population can reduce infections, and other studies that do not see any positive effect. It is important to look at the studies carefully, and see what exactly they measured, and how they measured it. I'll talk about just one study as an example, where they looked if wearing facemasks would protect others in the household if a child had a respiratory illness. The study found no effect, but it also found that only 21% of the participants used the masks often or always. If you don't use the mask, it does not work! They also went on to look specifically at the subgroup of people who did wear the mask most or all of the time, and did find a protective effect.

Since surgery masks and respirators are in short supply in the US and Europe, the very limited supplies should absolute be left to where they are needed most: hospitals and doctor's offices. But what about self-made masks? Do they work? Some doctors and official will simply state "they don't work", but what they actually mean is "they do not work nearly as well as properly fitted and used surgical masks and respirators". But it turns out that even the CDC recommend using self-made masks if nothing else is available:

Advice from the CDC website to doctors and hospitals
when no masks are available

That is for good reasons: multiple studies have shown that selfmade masks work to some extend - not as well as "proper" masks, but better than nothing. Here are data from a study that looked at different materials:

For a easier-to-read article, check this web page.

Many of these studies look at how well masks work at how well masks absorb small particles like bacteria or viruses when breathing in. But that's just one way how masks work. For the COVID-19 epidemic, the more important aspect is that masks reduce infected people from spreading the virus. Instead of explaining, just look at this image, and consider that each drop can contain many millions of virus particles:

If you stay 6 feet away from this sneezing or coughing person, you will not get directly hit by most of the droplets, since they fall down. But they then land on the ground, or perhaps the grocery shelf in front of him! There, the millions of viruses sit and wait patiently for someone else to touch the shelf and pick them up. The SARS-CoV-2 virus that causes COVID-19 can be patient - it can "live" for many hours on various surfaces.

Now imagine the picture above with a mask in front of the face. it is really not hard to imagine the difference! For the droplets that are easily visible on a photograph, it is really not that important that the mask captures the tiniest particles.

Let's look at one more aspect: what happens after you touched one of the droplets that the maskless man above deposited in the supermarket shelves. Now, the virus is on your finger. No big deal, since it cannot infect you through your skin, you think? Think again! Here's a picture from a study how often we touch our face:

That's 3 touches to the nose, 4 to the mouth, and 3 to the eyes every hour on average. Touch any of these areas, and the virus gets transferred right into your body where it starts multiplying! We humans touch these areas once every 6 minutes, on average. We've done it all our life, never thinking about it, so that's a habit that is very hard to change.

If we are wearing a facemask, we cannot touch the nose or mouth directly. Sure, we could move the mask to do so, but that is not an old habit, and we can probably stop ourselves in time. That should reduce the touches to one touch every 20 minutes. Our chances of making it out of the supermarket without touching a "transfer area" just increased a lot! If the supermarket has disinfectant at the checkouts, or even better at various places throughout the store, even better!

The US surgeon general said "we don't have data for that". Well, now, it's obvious, is it not? Although he also did point out one thing: you should not adjust your facemask constantly, something people who do not use masks a lot may do. But every nurse and doctor has learned that, so others can, too.

So, while we are waiting to the governments to do something that will drastically increase mask production (something Taiwan started doing in January!), we'll have to make out own, or perhaps use a dusk mask we have around for sanding or painting. When you use the mask, be careful where you touch it: after a while, there may be a lot of droplets with virus caught on the outside, so don't touch the outside!

There are plenty of instructions for various self-made masks on Youtube and other sites. Here's one example that looks simple enough:

So, if you really have to leave your house, do what all people in the countries that have stopped the COVID-19 epidemic early do: wear a facemask to protect yourself and others!
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 Added April 3, 2020:

Since I wrote this post, things are changing in Europe and the US. Austria and other European countries have made mask use mandatory in public. Germany has not, but there is a strong movement under the #maskeauf tag to wear masks. In the US, the CDC is expected to suggest that everyone wears masks in public soon. Here's a great video in German about wearing masks:

The only thing I have to add is that studies have shown that the virus is also distributed by normal breathing, not just by coughing and sneezing. But masks reduce how much virus "escapes" in normal breathing, too (and how far it gets away). So make your mask and wear it!