Best scientific explainer I have seen on why we should all wear masks

[flamingdem]

https://medium.com/@Cancerwarrior/covid-19-why-we-should-all-wear-masks-there-is-new-scientific-rationale-280e08ceee71

The official recommendation in the United States (and other Western countries) that the public should not wear face masks was motivated by the need to save respirator masks for health care workers. There is no scientific support for the statement that masks worn by non-professionals are “not effective”. In contrary, in view of the stated goal to “flatten the curve”, any additional, however partial reduction of transmission would be welcome — even that afforded by the simple surgical masks or home-made (DIY) masks (which would not exacerbate the supply problem). The latest biological findings on SARS-Cov-2 viral entry into human tissue and sneeze/cough-droplet ballistics suggest that the major transmission mechanism is not via the fine aerosols but large droplets, and thus, warrant the wearing of surgical masks by everyone.

The surgeon general tweeted: “STOP BUYING MASK, they are not effective…”. The Center for Disease Controls (CDC) states that surgical masks offer far less protection than the N95 respirator masks (which also must be perfectly fitted and only professionals can do it). The CDC recommends that healthy persons should not wear masks at all, only the sick ones. These guidelines are not rooted in scientific rationales but were motivated by the need to save the valuable masks for health professionals in view of a shortage. But they may have had unintended consequences: stigmatizing those that wear masks in the public (you are a hoarder, or you are contagious!)

Contrast this with the cultural habit, the encouragement, or even mandate to wear masks in Asian countries — which have now “flattened the curve” or even have had a flatter curve from the beginning.

Sure, surgical masks, and improperly worn N95 respirator masks, do not offer perfect protection. But if the stated goal is to “flatten” the curve (as opposed to eradication of the virus), we have to abandon the black-and-white thinking, and embrace shades of grey. We cannot any longer claim that masks “are not effective”. We cannot allow the perfect to be the enemy of the good. What if a however partial protection afforded by leaky surgical or even self-made masks reduces transmission probability to an extent that is similar to that of the recommended (equally imperfect) distancing by more than 6 feet from each other or “not touching your face”? It could then double the impact of non-pharmacological intervention (NPI) on flattening the curve (FIG. 1).

https://miro.medium.com/max/2333/1*cJ7fMaWrzk0Nm4YKY2ClNg.png

FIGURE 1. “Flattening the curve”. Effect of mitigating interventions that would decrease the initial reproduction rate R0 by 50% when implemented at day 25. Red curve is the course of numbers of infected individuals (”case”) without intervention. Green curve reflects the changed (”flattened”) curve after intervention. Day 0 (March 3, 2020) is the time at which 100 cases of infections were confirmed (d100 = 0). The model is only for illustration and was performed in the SEIR-model simulator (http://gabgoh.github.io/COVID/index.html). The non-intervention model was fitted to these data points: a time period of twenty days in which the number of cases in the United States has risen from 100 (d100=0) to 35,000 (d100=20). Standard parameters were used (population size 330 M, Tinc=5.2 days, Tinf = 3.0 days but with the rather high value R0=5.6 in order to achieve the observed rate of increase of case numbers in the U.S. The curves are redrawn not to scale.

Since the CDC provides no scientific evidence for its statement that masks worn by the public “are not effective”, here we review the scientific support for protection conferred by surgical masks. We focus on mechanistic rationale (as opposed to epidemiological-phenomenological evidence). We conclude, by considering cough droplet ballistics and the latest research findings on the biology of transmission of the SARS-CoV2 virus (which causes COVID-19) that any physical barrier, as provided even by make-shift masks, may substantially reduce the spread of COVID 19. If we are soon to yield to the pressure to loosen lockdowns and allow limited social interactions to revive the economy, then public masks should have a role and could facilitate a middle-of-the-road approach.

The official recommendation by CDC, FDA and others that masks worn by the non-health-care professionals are ineffective is incorrect at three levels: In the logic, in the mechanics of transmission, and in the biology of viral entry.

I. THE LOGIC

Of course no mask, be it the tight-fitting NIOSH approved N95 respirator mask or the loosely worn surgical mask, provide perfect (“100%”) protection. But imperfect protection does not mean “completely useless”, much as a glass not full need not be empty: I would gladly accept a glass of water filled to 60 % when I am thirsty. Absence of evidence (of protection) is not evidence of absence. But in our binary world, the official message that surgical masks are “not effective” may have sent the wrong message: that they are absolutely useless. Sadly, with the black-and-white picture painted by officials, the discussion about the effectiveness of masks has been stifled, and with it the possibility of incentivizing industry to ramp up production of these 75 cents-a-piece protective devices.

But with the declared goal to “flatten the curve” (and not to totally eliminate the virus) we have a “relative” as opposed to absolute goal, which places the notion of “partial protection” in a new light. In principle, one could compute the extent Y of flattening of the curve given a partial protection by X % as conferred by mask. But for that we need to first understand the mechanics and biology of transmission in detail.

II. THE MECHANICS

How viruses that cause airborne diseases are carried by droplets from person to person is a complicated, understudied matter. Droplets can (for this discussion) be crudely divided in two large categories based on size (FIG. 2):

https://miro.medium.com/max/1400/1*m_a-cX7BpzAOg5YpyDa_ZA.png

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[Skittles]

1. if medical folk cannot get them

how do they expect "everyone" go have them, and a new one every day at that

[flamingdem]

2. People are making them and it should get easier to

get masks as the shipments come in. N95 masks and lots of other masks are reusable if sanitized with alcohol or not used for 24 hours. I'm not 100% sure on that but have read it.

[triron]

4. Makes total sense. I have one (N95) I wear when I go grocery shopping.

Got it on ebay.

[pnwmom]

6. Even a bandanna or homemade one out of 2 layers of t-shirt material helps

to reduce transmission. There are even designs online for making them from paper towels and rubber bands.

[Cha]

3. TY for this, flamingdem..

I ordered some online last night.

The bus driver was wearing one yesterday and all the people at the health store I went to were wearing mandatory masks.

StaySafe!

[Grokenstein]

5. A perfect example of making "perfect" the enemy of good.

I have a very old N95 mask that had been sitting in my junk drawer. It has an extra thick inner liner (bought at a hardware store for work with particulates). It's not fit for medical use but damn straight I'm going to use it; some of my co-workers absolutely refuse to grasp the concept of "distancing." Strangers on the bus understand it better. I'll wash it or hose it down with disinfectant every day. It's better than just hoping idiots stand the hell back.

[Merlot]

7. Thank you for posting this helpful information

This is what I've suspected all along. It makes no sense to say that we have to keep 6 feet apart, but that the virus is only spread by touching things and then touching your face.