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Face masks effectively limit the probability of SARS-CoV-2 transmission

science.sciencemag.org

141–150 of 387 posts

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#141
For those of you who haven’t seen the slowmoguys video about talking with and without a mask this is good:

https://youtu.be/gZ66wJFD3bs

If you want to skip the technical lighting bits then jump to the 4 minute mark. It’s difficult to argue against footage like that and it makes you wonder why some people take off their masks to talk.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#142
post #71

Earlier quoted context omitted.

Bless your soul, but what I've learned from the way we handled the pandemic worldwide (and are still handling it) is that information that's readily available and should in theory reach everyone, flows ridiculously slowly, even among specialists and political figures, it's easily corrupted and distorted, and a loud ignorant minority counts as much in the public discourse, as the voices of millions of reasonable peopl…

Absolutely. Considering how long it took CDC and WHO to even acknowledge airborne transmission, even though the Chinese were very clear about it from very early on. https://www.nytimes.com/2021/05/07/opinion/coronavirus-airbo...

"even though the Chinese were very clear about it from very early on" I'm not sure this adds as much credibility as you seem to think. See (for example) - propaganda videos of people dropping dead in the street in Wuhan in early 2020.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#143
post #112
post #91

Earlier quoted context omitted.

And even the "masks make it marginally harder to exercise" is likely wrong. The winner of the 10,000m race at the 2019 USA Track & Field Championships wore a mask against his pollen allergies. [1] Worn properly, they just disappear. I wear N95s a work for many tasks, and they are mildly distracting for a few minutes, then I forget about them. Even more so now with wearing them for the pandemic. Yes, education about m…

According to that article, the winner of the 10,000m race wore a mask to protect against his allergies for the first 4,000m, by which point it was just too uncomfortable to continue wearing: "Rupp said Salazar told him to “wear it as long as you can. As soon as it starts to get real hot or uncomfortable, or starts to stick and get sweaty, throw it off.” The mask came flying off after 4,000 meters. But Rupp was conten…

Right, and during that time, he was respirating at around 20X the rate of you or I sitting here.

1 MET, or Metabolic Equivalent Task, is about 3.5 mL of oxygen per kilogram per minute, which is roughly equivalent to the energy expended when sitting quietly. [1]

The Vo2max of high-level athletes runs up to 97.5mL/kg [2]

Sure, he used it for 'only' 40% of the race.

In a national championship where fractions of a percent of O2 uptake make the difference in winning.

The point is that he still wore it, running in the pack of a national championship, for nearly two and a half miles (400m=2.585mi), over 11 minutes, respirating at a level that you literally cannot imagine if you can post that comment.

The mask neither slowed him enough to take him out of contention, nor did it create sufficient oxygen debt that he could not win.

IOW, the mask had a completely marginal effect at levels of respiration more than an order of magnitude beyond any ordinary activity.

Moreover, since air resistance increases roughly with the square of velocity, a first approximation of any mask drag or throttling he experienced vs normal respiration is not 20X, but more like 400x what a normal person would experience.

And even your own citation points to it being "uncomfortable, sticky or sweaty", in the context of a national championship race, not being any kind of oxygen hinderence.

And yet you want to claim that this can be ignored because he didn't wear it the whole time.

So, yes, everyone knows that masks can be mildly uncomfortable, even during exercise. But they are a helluva lot less uncomfortable than enduring that respiratory/vascular disease, and a lot more ethical than spreading it.

[1] https://en.wikipedia.org/wiki/Metabolic_equivalent_of_task

[2] https://www.topendsports.com/testing/records/vo2max.htm

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#144

This entire study seems to be centered around a theoretical, mathematical model, and I didn't see any attempt to actually validate that model. Basically, the authors seem to assume that the virus behaves according to their formulas, and show that under their assumptions, face masks work, but don't actually prove that their assumptions match reality - or did I miss something?

Nope. It's circular. We need actual tests in the wild, not models.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#145

This isn't a study; it is a mathematical model [1]. > Here, we develop a quantitative model of airborne virus exposure that can explain these contrasting results and provide a basis for quantifying the efficacy of face masks. We show that mask efficacy strongly depends on airborne virus abundance. Based on direct measurements of SARS-CoV-2 in air samples and population-level infection probabilities, we find that the…

Here is a recent published review for those seeking a more comprehensive and complete evaluation of the literature:

Howard, Jeremy, et al. "An evidence review of face masks against COVID-19." Proceedings of the National Academy of Sciences 118.4 (2021).

https://www.pnas.org/content/118/4/e2014564118

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#146
post #75

Earlier quoted context omitted.

Indeed this is the money paragraph: "The effectiveness of masks, however, is still under debate. Compared to N95/FFP2 respirators which have very low particle penetration rates (around ~5%), surgical and similar masks exhibit higher and more variable penetration rates (around ~30-70%) (2, 3). Given the large number of particles emitted upon respiration and especially upon sneezing or coughing (4), the number of respi…

The mistake that many people make, and that I think you're implicitly making here too, is this notion of "controlled study". If the study denies the result seen time and again in real life, perhaps the study isn't studying correctly.

How many agains makes the study wrong

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#147
post #142

Earlier quoted context omitted.

Absolutely. Considering how long it took CDC and WHO to even acknowledge airborne transmission, even though the Chinese were very clear about it from very early on. https://www.nytimes.com/2021/05/07/opinion/coronavirus-airbo...

"even though the Chinese were very clear about it from very early on" I'm not sure this adds as much credibility as you seem to think. See (for example) - propaganda videos of people dropping dead in the street in Wuhan in early 2020.

Not sure what you're getting at. Preprint for this paper was out in Apr 2020:

https://pubmed.ncbi.nlm.nih.gov/32240078/

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#148
post #75

Earlier quoted context omitted.

Indeed this is the money paragraph: "The effectiveness of masks, however, is still under debate. Compared to N95/FFP2 respirators which have very low particle penetration rates (around ~5%), surgical and similar masks exhibit higher and more variable penetration rates (around ~30-70%) (2, 3). Given the large number of particles emitted upon respiration and especially upon sneezing or coughing (4), the number of respi…

> On the other hand, "observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease 2019 (COVID-19) (7–9)." So how to explain these contrasting results and apparent inconsistencies? My hypothesis regarding surgical mask prevalence and how it correlates with better virus control: People who wear masks--however effective they m…

It’s worth also considering the case of ski helmets. Since these have became common on the slopes head trauma has actually increased because wearers take more risks.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#150
post #75

Earlier quoted context omitted.

Indeed this is the money paragraph: "The effectiveness of masks, however, is still under debate. Compared to N95/FFP2 respirators which have very low particle penetration rates (around ~5%), surgical and similar masks exhibit higher and more variable penetration rates (around ~30-70%) (2, 3). Given the large number of particles emitted upon respiration and especially upon sneezing or coughing (4), the number of respi…

The mistake that many people make, and that I think you're implicitly making here too, is this notion of "controlled study". If the study denies the result seen time and again in real life, perhaps the study isn't studying correctly.

If we fully understood what was happening in real life, we wouldn't need studies.
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