Masks to Prevent COVID-19?

Since January of 2020, over 450,000 deaths have taken place across the globe with the virus being present in virtually every country.  The virus in question is a novel coronavirus named SARS-COV-2.

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The virus is deadly and seems to possess a wide variance of symptoms, morbidities, and  other complications; it is particularly threatening to those who are elderly or suffering from certain pre-existing conditions. In fact, the case fatality rate (CFR) is likely to arrive at about 2-3% (source), and the infection fatality rate (IFR) will likely be much lower at about ~0.79;  but a single IFR or CFR is not particularly useful given the wide variance of effects it has on groups of potential patients.

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One major challenge around controlling this pathogen is rooted in the contagiousness and asymptomatic spread. SARS-COV-2 maintains a reproduction number close to about 5.0  -making the virus very aggressive  (a typical influenza virus possesses a reproduction number (i.e. R0) range of about 2.0-3.0) and difficult to manage with standard tracing and testing -a reproduction number this high allows for rapid and large-scale outbreaks to occur in a short time period (see superspreader events where the R0 can exceed 5.0 by orders of magnitude), and this is compounded with about 40% of carriers are asymptomatic. 

Finally, another difficulty in managing SARS-COV-2 infectiousness in a way that lowers the R0 to a reasonable level, which is R0 <1.0,  is how it is spread. There has been considerable debate on this subject. Initially, the US NID and CDC declared that the virus transmission was due to contaminated surfaces, and downplayed the  other potential routes of transmission. Moreover, the same government entities dismissed the use of other precautionary measures such as mask use with the surgeon general claiming that masks did not prevent the spread of the illness (source), and Dr. Fauci later admitting that the government lied about masks (source).

So, getting to the point: do masks work?  The answer to this question is actually easy, but getting people to understand the simplicity of why the answer is true is a serious challenge. Over the last few months (since January 2020) , I have been arguing that people need to take rapid and heavy-handed precautionary measures, but my assertions are usually met with serious disdain much like what Gov. Gary Herbert (R, UT) experienced when he recently encouraged mask use:

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Most faultfinders of mask-use leverage a number of claims to reinforce their belief that masks cannot possibly prevent  the transmission of an airborne illness like COVID-19 -the following list details these objections:

1) An article published as a comment with the University of Montana (source)

2) A research article that examines the evidence for mask use (source)

3) An additional research article (source)

Before addressing these articles and the “evidence” they don’t have, let me make something very clear:

Absence of evidence is not tantamount to evidence of absence 

All the major articles or stories involving why masks wont work is due to the research paper often claiming “there is little scientific evidence supporting mask use to prevent…” -that actually is not very informative. In fact, that claim is not saying “there is evidence that masks do not prevent…”. This is where most people get confused. They seem to think that a lack of empirical knowledge of a fact tends to promote the potential that such a fact does not exist, and we know, very well, that such is not the case. All sorts of things are not empirically verifiable at certain points, but are nonetheless true.

So, on that note, the question that we have to answer is: can mask-use actually be an inherent  mitigator of transmission risks? The answer is undeniable -that is, undeniable that masks mitigate a risk.  This mitigation is due to various interesting effects around how masks affect the probability of transmission. In fact, all the research questioning mask-use efficacy (see points (1) and (2)), also admit that there are reductions in risk that are noticeable and immediate, but often small at about 10-60%. Continuing with that specific line of thinking, let’s take a absolute reduction of 25% (where p=1/4); what does that work-out to if both people use masks (something that almost all the studies ignore)?  Well, Nassim Taleb has already shown the mathematical result to be significant,

“…with p=1/4 we get R0′= p² R0 . The drop in R becomes 93.75%! You divide R by 16! Even with masks working at 50% we get a 75% drop in R0.”

The mistake that most studies commit is a complete lack of understanding about the compounding effects across ensambles and how that impacts the virus’s reproduction number over a population set. While the individual benefit of using a cloth mask may be low as a prevention, if we had everyone use them, the risk would fall precipitously and the overall benefit would be significant.

How much would the risk fall? Well, since we have fallen upon the fact that use across an ensemble tends to exhibit compounding effects, we can estimate (since many countries are requiring masks) what the effects are based on mask efficacy and compliance:
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The above image shows, based on current evidence and statistical models, that we can reasonably and with very low cost, lower the R0 by ensuring a high compliance of mask use. Even with a 50% effective mask, and 100% compliance, we crush the R0 to less than 1 (source)!

Now, back to the issue in (1) around masks “filtering” particles. There is this odd hyper-focus on filtering efficacy by respiratory specialists and air-filter engineers as it relates to illness transmission. Often the detractors claim that the virus is smaller than the pore size in all masks even the notorious N95 and this inhibits their effectiveness. Honestly I don’t know why this is an issue for several reasons: first, the virus is rendered in an aerosol that is often much larger than the pore size of an N95, and, even with a cloth mask, the rate of attack (the dose of virus) of the number of virus you are exposed to is significantly better than no protection at all; second, a mask helps slow the amount of virus an infected victim can render into the environment -see the following image:

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With just a paper towel, the amount of particles are decreased by over 95% -with about 4% being expelled as a nasal discharge. This study showed that with a full nose to mouth mask, the amount of particulate is minimized by about 90%! Considering a rate of attack of, say, 60% with a virus load of 10^6, a further decrease by 90% is MASSIVE which  not only impacts transmission rate, but can mean the difference amid serious illness and mild illness. Some may be tempted to say, “well… why does this matter if you are not sick. I know I am not sick, so I should be able to go without a mask” -this is a question I will address later, but as it relates to this study is that speech is a potential medium of transmission (source)  given the replication of SARS-COV-2 in the upper airway; and, thus, by evaluating droplet dispersion using coverings, we can get a better sense of the masks ability to protect others.

There, derived from (2), is a claim that only the best respirators or masks provide any benefit; thus, if you are not using at least a N95 or greater, you are not benefiting. This is completely false (source). Studies have shown that even homemade cloth masks slow the dispersion of virus particles -thus, minimizing the overall rate of attack, and benefiting others who are also using masks.
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Some other sources have shown that face coverings reduced transmission in households up to 80% (source) and simple masks are also useful (source).

Now, how is mask mandates working for countries who have them in-place? First, (source) in countries with universal mask-wearing, per-capita coronavirus mortality increased by just 5.4% each week compared with 48% each week in remaining countries! Screen Shot 2020-06-21 at 2.48.40 PM

Second, all the countries that have implemented masks mandates and have maintained high compliance, have done much better than those that do not have similar mandates or compliance. Take for instance, Thailand, that has a high organic use of masks since about March 16th of 2020:

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Now, look at Vietnam, that mandated masks in March:

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These images possess general trends that are seen across all mask-mandated countries -there is one exception, however, and that is Saudi Arabia (SA). In SA, the mandate was imposed the last few days in May with formal execution of the imperative around June 10th. There was a rapidly growing outbreak that persisted since the end of May, but since the mask mandate,  there is some encouraging signs as the virus’ transmission rate falls (SEE UPDATE SECTION -END OF POST):

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SA has had challenges with certain business compliance and religious groups, but now that the mask use is in full-swing, I expect the decrease they are seeing to continue. Let’s now compare that to the US:

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Most of the lull from the end of April to the first week of June is likely due to the same equifinal effects of the both the lockdowns and serious precautionary behavior of certain states due to the fact that outbreak manifestation takes about 24-30 days to be fully realized. The uptick since the beginning of June is not unusual, over 70% of Americans shun masks .

There is even more localized data showing mask efficacy. If we look at Colorado that had city-based mandates in effect at around the first of May, and moved to state-mandate end of July  for the most populous cities, we see a very similar trend (which only signals potential effect -not causation):

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Finally, there is this claim from certain political positions that asserts something to the effect that “you don’t have the right to force me to use a mask” or that the mandate violates the tenets of liberty. I don’t think the reasoning works -let’s take a look at the fundamental principle that supports almost all (logically) arguments from liberty -the Non-Aggression Principle. The principle asserts that initiating or threatening any forceful interference with an individual’s life or property, is inherently immoral. This principle is often considered a fundamental element of conservatism and libertarianism in the United States (source).  By not using a mask, you violate the principle in two major ways:

1) You risk harming them and threatening their lives by spreading a lethal virus to them.

2) By not using a mask, you are forcefully augmenting the individual risk of harm the other person is experiencing (which results in (1)).

Now, some will argue that they are not initiating any aggression because they do not possess the proper epistemic conditions to be said to actually aggress against another -however, this does not hold water. The fact that there could be up-to 20% to 40% of carriers are either asymptomatic or pre-symptomatic, you could easily, at any time, be a carrier or spreader of the illness (source). Thus, you are obligated to take all precautions not to violate or harm others given that you cannot completely know if you are not really infected.

The foundation of a moral society is one that protects the least among them. It is a society that willingly takes precautions to ensure that the elderly, the sick, or the helpless are protected -particularly, when the amount of investment involved is not ruinous to the he who is obligated to protect them.

So, to answer your question: are masks effective in minimizing COVID-19, the answer is YES.


1) Source on Dr. Fauci’s deception around masks (source).

2) A very telling bit of evidence where a hairdresser and her partner were both COVID-19 positive and had attended to 140 clients while infected with SARS-COV-2 and not a single client was infected due to policy of both the hairdresser and client having to use masks (source). The probability of this occurring without masks with an R0 from 2 to 5 is almost zero! That is, without masks, we should expect that at least 110 or more should have been infected; thus, mask use blunted the R0 to ZERO in this case!

3) More evidence of aerosol transmission (source)

4) An NPR article highlighting the general evidence for mask use (source)

5) Some very nice explanations and evidence for the effects of maks use (source)

6) There is this concern that masks may not have the overall benefit that proponents suggest. Specifically, there is an argument that with incorrect use of protective personal equipment (PPE), that the reduction in risk of transmission due to mask use may be off-set by the mishandling of PPE -namely, that people touch their mask incorrectly, that they may use the mask incorrectly, or that they many not clean or dispose of the mask correctly resulting in contaminating their hands and, thus, infecting themselves with the virus.

To respond to this, let me say that this is a good issue to consider. We need to take serious precaution with our PPE and how we take it off and on while we maintain handwashing and the like. However, I do not believe that the number of people infected due to misuse is going to equal the number of people infected by lack of mask use. That is, the reproduction number of the virus is greater with precautions such as hygiene  and disinfection protocols with no masks than it is masks alone. So, if I had to make a bet, I would be that masks are sufficient to minimizing the pandemic over hygiene/disinfection alone.

Now, given that, I think people still fall under the idea that masks are acting as a one-way protection device. This is NOT how I am looking at masks -their efficacy is two-way: when both people use masks the risk of virus in the environment declines significantly and the exposure to that virus by others is minimized (source). This has a ton of spillover effects -particularly when a carrier uses a mask-  (a) minimizes rate of attack on others and lowers severity of infection or eliminates the risk, and (b) lowers the bio-burden on surfaces (virus falling out of aerosol and contaminating surfaces as seen in studies in the ICU) which lowers transmission via those surfaces.   Thus, if we have everyone using masks, the total bioburden diminishes and drives the reproduction number to less than one -masks may indeed be sufficient regardless of misuse.

7) Another update:

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This dovetails with other studies on mask compliance and reproduction number; over time, and with robust mask use, you can effectively end the pandemic.

8) BYU has assembled a report on research supporting mask use –here. Some of the key elements they bring up focus on the how masks contain infection and, hence, lower the risk of increasing the viral burden in the environment. They also provide the visual proof of lowering the burden (this should break the perceptions around correlation and causation that anti-maskers focus on -we have empirical evidence).

9) Update on Saudi Arabia ( you can see more of the trend here)

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The decline since the mask mandate has been consistent. We are seeing this elsewhere. 

10) More evidence in the healthcare setting here.

11) A very interesting observational case where those who used face shields did not avoid an outbreak, but those who used masks were left unscathed (here).

12) Between January 24, 2020 and February 15, 2020, an outbreak of COVID-19 occurred among 335 passengers on a flight from Singapore to Hangzhou in China; 15 already-infected passengers on a full plane of other individuals using masks, and only a single new infection took place -this man was sitting next to an infected person, and was not using a mask at various points (here).

13) Some overview of map prevention from The Lancet (here)

14) As of 23 Oct 2020, new data showing mask effectiveness has been produced (by CMU): Screen Shot 2020-10-23 at 10.48.29 AM

Not a bull-shit correlation -you can test that by just looking and seeing if a few points determine the trend and if removed, the whole think looks bonkers. In this case, even if you removed WY, SD, ND, DC, MA, RI, FL, LA the regression line would be almost untouched. This helps us understand that the effect us robust.

One thought on “Masks to Prevent COVID-19?

  1. You are a crazy. Fucking crazy. Masks can’t filter virus. They are smaller than what a mask can filter.

    It’s about my rights. Masks are a way to force people to abandon their rights. Like forcing a woman to use a shirt.


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