The Case for Mask Wearing

We outline the case for wearing masks - and for everyone to wear masks.

Table of Contents

  1. Why should we wear masks?
  2. Masks work to reduce the spread of COVID-19
  3. Asymptomatic transmission
  4. Masks protect your community
  5. Masks protect you
  6. Almost everyone has come around on masks
  7. Case study: Singapore vs. Hong Kong
  8. Scientific consensus
  9. Further reading
  10. Footnotes
  11. Comments

Why should we wear masks?

The virus doesn't respond to bravery and isn't impressed that you won't be intimidated by it. It has no feelings, no goals, no interest in whether you're afraid of it or not. Why not take advantage of the easiest defense strategy you can find?

If that's not enough, here are much more detailed arguments.

Masks work to reduce the spread of COVID-19

Masks are perhaps the cheapest and most effective weapon we have to fight this viral pandemic - and any other airborne disease.

A recent paper places the economic value of a single mask at $3-6,000:

The Case for Universal Cloth Mask Adoption & Policies to Increase the Supply of Medical Masks for Health Workers April 1 2020
The Case for Universal Cloth Mask Adoption & Policies to Increase the Supply of Medical Masks for Health Workers April 1 2020

Because:

  • "People infected with the SARS-COV-2 virus can have minimal symptoms or can be completely asymptomatic. Thus, seemingly healthy people, including young people, are spreading the virus by transmitting it to others."
  • "Masks, including cloth masks and surgical masks, have measurable efficacy at preventing infected people from transmitting viruses to others."

Read more in this Twitter thread by one of the paper's authors.

While most people are by now aware that SARS-COV-2 is transmitted through droplets in the air, it may not be obvious what that means in reality. Those droplets travel far and linger long after being expelled by an infected person.

Chinese scientists discovered infections occurring at a distance of 4.5 meters (almost 15 feet), with infected droplets lingering in the air for half an hour.

Viral transmissions on a Wuhan bus
Coronavirus can travel twice as far as official ‘safe distance’ and stay in air for 30 minutes, Chinese study finds

Asymptomatic transmission

We've already established that masks reduce spread of COVID-19 partly due to the incredible numbers of carriers who show no symptoms.

This is such an incredible and increasingly researched area that we've split this section off into its own article.

Masks protect your community

We all have someone we care about in a vulnerable class. That includes far more people than you might imagine: besides the elderly, anyone with respiratory problems like asthma, a heart condition (which are often undiagnosed), Parkinson's, diabetes, cancer treatment, suffering from autoimmune conditions or simply overweight (that factor alone accounts for 70 million people in the United States), is vulnerable.

Even if you're not convinced that masks will protect you from infection, they could save others from yours. It's simply selfish and irresponsible not to wear a mask, prolonging the economic downturn for everyone.

Besides you wearing a mask yourself for the benefit of others, you can distribute masks to those who don't have them or can't afford them.

If you're in the United States, the PPE Coalition lists ways you can help with supply.

Other places to donate:

If you can afford to, give them away to essential workers: besides nurses and doctors, consider the underpaid cashiers, delivery drivers and technicians who never signed up for this kind of risk that they're now absorbing to keep the rest of our lives running comfortably indoors. Their level of exposure is high. You'll be safer if they're safer (we've been giving delivery drivers masks on top of their tips).

Give them to family and friends who are skeptical about the benefits of mask wearing; they'll be grateful to have some on hand when they do eventually come around.

Models: how it looks if many people wear masks

Models show that, with widespread mask wearing, the spread can be slowed dramatically.

Number of infected cases with no masks, surgical masks and N95s in a simulation
Figure A Number of infected cases with no masks, surgical masks and N95s in a simulation
Three cases are shown when 10%, 25% and 50% of the total population wears masks
Figure B Three cases are shown when 10%, 25% and 50% of the total population wears masks

Mask wearing reduces other infections so hospitals are less strained

Another interesting effect of mask wearing has been observed in Hong Kong: the rate of all other infectious diseases has been reduced, lessening the strain on hospitals. Mask wearing in Hong Kong, which was heavily impacted by SARS, became nearly universal during this pandemic, despite the government insisting it wasn't necessary.

According to Dr HO Pak Leung, it is the combined efforts made by HKers... Not just the case of Coronavirus, basically all respiratory virus infections dramatically dropped since Feb, where basically 99% of HKers wore masks against the govt appeal not to wear masks unnecessarily.
Via Twitter, @lokinhei, "According to Dr HO Pak Leung, it is the combined efforts made by HKers... Not just the case of Coronavirus, basically all respiratory virus infections dramatically dropped since Feb, where basically 99% of HKers wore masks against the govt appeal not to wear masks unnecessarily."

Mask wearing is a true community effort

The great thing about masks is that you don't need permission to wear them (in most places). You don't have to wait for incompetent government officials to reach a consensus or take action.You don't even have to buy them: making your own mask is far better than nothing. The more people who wear them, the more the stigma against masks is reduced: a positive feedback loop. As one official said in the 1918 Spanish Flu pandemic, "Better be ridiculous then dead."

Your own safety depends on others being safe. Just as you aren't in traffic - you are the traffic - you are someone's "other" as they are yours.

A sign outside of a restaurant in Thailand
A sign outside of a restaurant in Thailand

Masks protect you

And not only against COVID-19. Masks protect you against air pollution and, notably, many infectious diseases.

Masks keep you from touching your face, a common way for the infection to spread. The "virus is viable for up to 72 hours on plastics, 48 hours on stainless steel, 24 hours on cardboard, and 4 hours on copper. It is also detectable in the air for three hours."

Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1
Scale is in hours. From: Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1

The dose makes the poison

Even if the mask fails to prevent infection, it's likely to reduce the viral load - that is, the amount of the virus you're exposed to.

A study on SARS (another novel Coronavirus) concluded that initial viral load was a factor in the severity of the illness:

Initial viral load and the outcomes of SARS
Initial viral load and the outcomes of SARS

There was a fascinating study on the spread of SARS within an apartment building where early cases were detected. For a research paper, it's a pretty gripping read. Cases nearer to the initial (index) patient on block E7 had a higher viral load: In E7, patients who resided within a few stories of the 16th floor had higher viral loads. For cases in neighboring E8, the distribution of patients and viral loads was random.

Viral Load Distribution in SARS Outbreak [Figure left] Viral Load Distribution in SARS Outbreak [Figure right]
Viral Load Distribution in SARS Outbreak

The death rate for patients near the source of transmission were much higher.

The overall case death rate among the 79 patients was 24.1%. The highest rate was in block E, which accounted for 79% of all deaths, while the death rate in patients living in E7 (the same block as the index patient) was 70% (7patients). This rate is significantly higher than in other units (p = 0.001 by χ2 test). The index patient was one of the few patients from E7 who survived the disease.

The method of transmission with the block was never fully determined. Like any good horror film, it left an opening for the sequel, SARS 2.

Viral Load Distribution in SARS Outbreak [transmission source]
Viral Load Distribution in SARS Outbreak

Another paper concludes that the culprit was an exhaust fan driving air through the sewage system into neighboring apartments.

This isn't the case only with SARS. Studies on HIV reached similar conclusions:

As with the SARS-coronavirus of 2003, the severity of #COVID19 likely depends on the viral load upon initial infection. A high initial load may overwhelm your immune system before it's able to mount a response. Orange line=sneeze to the face Blue line=touching infected surface
Via Twitter, @JamesTodaroMD

And the flu:

Here’s a paper demonstrating correlation of flu dose with severity of subsequent infection in mice

Almost everyone has come around on masks

Most countries, scientists, and news organizations have reached the conclusion that the closer we get to universal mask wearing, the better. Everyone but the WHO. Who knows why. Though even they're now re-evaluating their position.

There are fewer and fewer #antimaskers by the day.

Below is a partial list of converted mask skeptics, taking the example of mask-wearing countries where the pandemic is best controlled - South Korea, Hong Kong, Taiwan, and others.

  • Sweden changed their stance on masks, citing new information (this is actually very old information).
  • Canada
  • Germany is now recommending mask wearing.
  • Peru has been handling the crisis effectively and mask wearing is now mandatory in public.
  • Austria has made mask wearing mandatory, but much of the population remains skeptical.
  • Now mandatory in Bulgaria.
  • Israelis required to wear masks.
  • The South African Minister of Health made a somewhat contrite statement in support of masks.

Case study: Czechia and Austria

A telling, but not conclusive, case study is the contrast between Czechia and Austria.

On March 16th, both Austria and Czechia started nationwide quarantines. One difference was that Czechia's quarantine included masks. Compared to Austria, the growth of Czechia's new daily cases #Covid_19 has relatively slowed.

On March 16th, both Austria and Czechia started nationwide quarantines. One difference was that Czechia's quarantine included masks. Compared to Austria, the growth of Czechia's new daily cases #Covid_19 has relatively slowed. #Masks4All
Via Twitter, @adamcchang

Case study: Prato, Italy

Another instructive case is of the Chinese community in Prato; Italy's largest. Among Chinese resident in Prato there isn’t even one case of COVID contagion because they, in contrast to their Italian counterparts, took early, strict adoption of infection-control measures.

After emerging from his self-quarantine, he ventured outside in mask and gloves. He said the few other Chinese on the streets also wore them, anxious not to spread the virus to others. “My Italian friends looked at me oddly. I tried many times to explain to them that they should wear them ... but they didn’t understand,” Luca said. “When I came back to Prato, no Italian authority told me anything. We did it all by ourselves. If we had not done it, we would all be infected, Chinese and Italians.” “We Italians feared that the Chinese of Prato were to be the problem. Instead, they did much better than us,” said Renzo Berti, top state health official for the area, which includes Florence. “Among Chinese resident in Prato there isn’t even one case of COVID contagion,” he said, referring to COVID-19, which has killed almost 12,000 people in Italy, more than in any other country. Ethnic Chinese make up about a quarter of Prato’s population, but Berti credits them with bringing down the entire town’s infection rate to almost half the Italian average — 62 cases per 100,000 inhabitants versus 115 for the country.
From zero to hero: Italy's Chinese help beat coronavirus

United States

As late as February 27th, Dr. Robert Redfield, the Director of the U.S. Centers for Disease Control and Prevention was asked, "should you wear a mask if you're healthy?"

Dr. Robert Redfield, the Director of the Centers for Disease Control and Prevention
Dr. Robert Redfield, the Director of the Centers for Disease Control and Prevention

To which he replied:

"No... because I do see people feeling the need to go buy masks... there's no role for these masks in the community"

Thankfully, the United States will be recommending mask wearing, though with a signature twist, as President Trump insists that scarves are superior to masks (scarves are thicker).

This is a welcome reversal after the US Surgeon General recommended against universal mask wearing:

Seriously people- STOP BUYING MASKS!  They are NOT effective in preventing general public from catching #Coronavirus, but if healthcare providers can’t get them to care for sick patients, it puts them and our communities at risk! http://bit.ly/37Ay6Cm
Twitter, @Surgeon_General

Mainstream publications named and shamed celebrities for wearing masks. Others went as far as to say that wearing masks "could put you at greater risk for coronavirus."

Now California is fining residents $1,000 for failing to wear masks outdoors, much as it did in the 1918 epidemic:

In the 1918 flu pandemic, not wearing a mask was illegal in some parts of America
"In the 1918 flu pandemic, not wearing a mask was illegal in some parts of America. What changed?" (CNN)

The boffins at Vox recanted their jibes after initially coming out against masks, and are firmly pro mask.

2/ Oh, and face masks? You can pass on them. Masks are only useful if you have a respiratory infection already and want to limit the risk of spreading, or if you’re working in a hospital in direct contact with people who have respiratory illnesses.⁣ http://bit.ly/2PzvrSl
Via Twitter, @ComfortablySmug

Everyone eventually comes around to the same realization.

Case study: Singapore vs. Hong Kong

Warning: this is all speculation

Contrary what you may have seen on social media, Singapore is not a mask-wearing country. Their success in combating spread has come from diligent quarantine, testing and some of the best tracking and tracing in the world.

You and hundreds of millions of people have probably seen this graphic I composed as part of a long research document.
Via Medium, @jperla

A recent survey (February 26 to March 11, pending publication) found that only 6% of Singaporeans wear masks every day and 58% hadn't worn one in a week. But still better than in the West: 82.6% say they wear one when they're knowingly sick.

While Singapore has gone from recommending against universal wearing to handing masks out to its citizens due to concern over asymptomatic transmission, compliance is not at Hong Kong levels and the lag time has potentially revealed a marked difference in new case counts between the two.

Hong Kong daily new cases Singapore daily new cases
Via Twitter, @Birdyword

Other factors endemic to Singapore are the large number of migrant workers who are suffering in crowded dormitories (of the 942 new cases reported on the April 18th, 95% were among migrant workers in these dormitories) and the daily influx of commuters from neighboring and much more heavily afflicted Malaysia.

Advice from China

Gao Fu, director general of the Chinese Centre for Disease Control and Prevention, is clear on the necessity for mask wearing. He says:

"The big mistake in the US and Europe, in my opinion, is that people aren’t wearing masks... This virus is transmitted by droplets and close contact... you’ve got to wear a mask, because when you speak, there are always droplets coming out of your mouth... Many people have asymptomatic or pre-symptomatic infections... If they are wearing face masks, it can prevent droplets that carry the virus from escaping and infecting others."

Here's a study from China on the size and distribution of droplets from coughing. The amount of distribution (that is, how far the droplets spread) is so much greater without a mask that the scale of the charts are completely different: without masks (left), the y-axis goes from 0 to 6000 droplets/cm3. With masks (right), it maxes out at 800 droplets/cm3.

The size distribution of the coughing droplet without mask The size distribution of the coughing droplet with mask
The Size and Concentration of Droplets Generated by Coughing in Human Subjects

Upcoming case study: Turkmenistan

Some countries are trying bold, alternative strategies. We'll check back in with them later to see how they do.

Turkmenistan has banned the word “coronavirus,” as police officers arrest people for wearing face masks or discussing the pandemic in public.
Via Twitter, @NPR

Scientific consensus

Study after study after study confirms that masks work. Not 100% of the time. But enough to save many lives and, with full compliance, even the global economy. An partial list of studies and white papers follows (the most thorough and conclusive is highlighted in red):

Study Conclusion
Physical Interventions to Interrupt or Reduce the Spread of Respiratory Viruses: Systematic Review From 2008, wearing a N95 mask is a 91% effective intervention to prevent SARS infection (beats 10x daily hand-washing)
Rational use of face masks in the COVID-19 pandemic (Lancet) "As evidence suggests COVID-19 could be transmitted before symptom onset, community transmission might be reduced if everyone, including people who have been infected but are asymptomatic and contagious, wear face masks."
Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic? "Our findings suggest that a homemade mask should only be considered as a last resort to prevent droplet transmission from infected individuals, but it would be better than no protection"
Respiratory virus shedding in exhaled breath and efficacy of face masks 5 year study "Our results indicate that surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals." More so for coronaviruses!
Surgical Mask vs N95 Respirator for Preventing Influenza Among Health Care Workers Surgical masks and N95 respirators work comparably well to reduce flu infection
Mathematical Modeling of the Effectiveness of Facemasks in Reducing the Spread of Novel Influenza A (H1N1) "Facemasks and hand hygiene were correlated with a 35–51% reduction in influenza-like illness." (Figure A)
Economic Analysis of the Use of Facemasks During Pandemic (H1N1) 2009 Simulation showing that 25% mask compliance could lead to under 1m cases instead of over 100m (Figure B); if 50% use masks = $573b losses averted.
Modeling the Effectiveness of Respiratory Protective Devices in Reducing Influenza Outbreak Model: "80% compliance rate essentially eliminated the influenza outbreak."
Could SARS-CoV-2 be transmitted via speech droplets? All speech generates thousands of droplets. "A damp homemade cloth face mask dramatically reduced droplet excretion, with none of the spoken words causing a droplet rise above the background."
The Case for Universal Cloth Mask Adoption and Policies to Increase Supply of Medical Masks for Health Workers "...each cloth facemask generates thousands of dollars in value from reduced mortality risk. Each medical mask, when used by a healthcare worker, may generate millions of dollars in value"

Further reading

Many more studies can be found in the Masks4All Google Doc.

Papers about effectiveness of basic masks #masks4all
Papers about effectiveness of basic masks #masks4all

For less scientific reading, a list of articles in mainstream publications:

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