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

science.sciencemag.org

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

#261

Post by alvah »

slver wrote: post #260
alvah wrote: post #237

Earlier quoted context omitted.

There hasn't been a single case reported in the West, of anyone dying instantly in the street of COVID-19. Ergo, videos filmed within China, allowed by the authorities to be viewed outside China, purporting to show this scenario, are the very definition of propaganda.

We also saw videos of sick people left to die in Chinese hospitals from their own phone recordings. Is that also propaganda? And no, a video of something that isn’t what we thought it is, is not the definition of propaganda. Propaganda has a goal. This video doesn’t match a single goal China has. If it does name it.

I will politely decline your invitation to name any way the CCP has benefited from the last 14 months of havoc in the West. Feel free to carry on shilling for them.

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

#262

Post by beagle3 »

panarky wrote: post #229
__blockcipher__ wrote: post #163

Earlier quoted context omitted.

Except there is no convincing evidence that they actually do help others, and the whole theoretical mechanism is centered around catching large respiratory droplets which is at odd with the totality of evidence pointing towards aerosol being the dominant mode. I would add if droplet transmission is the dominant mode, which I very much doubt, then masks would still fail in a real-world setting when you look at the fac…

> no convincing evidence This MIT study [0] was pretty convincing. They conclude that "face masks can be an extremely effective indoor safety measure". For example: If an infected person was riding on a commercial airline with 100 other people, other passengers would be at risk of infection within 70 minutes. If all of the passengers wore masks, however, that space could be safe for up to 54 hours. [0] https://www.pn…

Basically all convincing evidence for mask use is models (like the linked article) and in vitro unrealistic tests; whereas in real world data, the best I could find wrt covid is 2% reduction.

Bacteria are a different matter, and possibly other viruses. But real world data about covid is that masks make very little difference either way, and are possibly harmful.

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

#263

Post by hermitcrab »

wyclif wrote: post #258
crocodiletears wrote: post #187

Earlier quoted context omitted.

In the US, it's more to do with the way the CDC's messaging throughout the pandemic than any rejection of the evidence concerning a mask's efficacy. People refusing to wear masks rarely question whether or not it works, and more to do with a low estimation of the disease's threat, as well as contempt for both the technocrats who chose to mislead the public about masks early on, and leaders who they believe are overst…

I think the CDC mis-messaging is one component of this. Another is that there is no long tradition of public medical mask-wearing in the West, unlike many parts of SE Asia. Public mask-wearing is new, exceptional, and somewhat alarming if you live in North America or Europe. Yet another component is that trust in the press and other public institutions was at possibly an all-time low in America at the time the COVID…

If you wore a mask in public in the UK before COVID, you would have got some very strange looks. They might have thought you were a criminal trying to hide your face. It seems fairly normal now though.

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

#264

Post by ppf »

epivosism wrote: post #59
AstralStorm wrote: post #8

As suspected, it's exactly a probability game. If there's few infectious particles sure to low concentrations (e.g. people distance or are outdoors), you would roll the 70% penetration chance fewer times, and result in very few particles reaching deeper into lungs too as the velocities are reduced. When very close to an active particle source, you'd roll the conditional probability dice many more times. The critical…

Yes. Crazy how hard it has been for people to get this: Imagine a bulletproof vest with three larger-than-bullet-sized holes in it. Say you know someone is going to shoot ten bullets at you - would you not wear the vest because "the attack vector can fit through the pores"? The point is people treat this as a binary 'safe' / 'not safe' switch, when actually risk is related to the distribution of exposure to dosage.

If we're talking about the size of the holes in a mask compared to a virus, then it would be more like wearing a "bulletproof" vest full of holes 10x bigger than a bullet.

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

#265

Post by beagle3 »

simpleguitar wrote: post #177
xkcd-sucks wrote: post #165

Earlier quoted context omitted.

I wear "n95" masks while sanding drywall, obviously trying to make the fit as good as possible, and still my boogers end up with tons of plaster in them. I would assume these particles to be bigger than any virion.

A properly fit N95 should block out all dust. If you are getting plaster in your nose, try different types of masks (folding), or a half-face respirator. One of the justification for not advising N95s to the public was the fact that most people don't know how to properly wear one. As if they couldn't be trained in a few weeks, or duration of the pandemic. Also, N95s filter out particles smaller than .3 microns (the 9…

Unless you have a valve, and hardly breath at all, exhaling pushes the N95 away from your face enough to let some unfiltered air in. There’s a similar (though smaller) effect with the thin paper valves, but regardless of how good the fit is, you need a much better valve than that to actually filter all air through the fabric.

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

#266

Post by kelnos »

ddingus wrote: post #182
solarengineer wrote: post #176

Earlier quoted context omitted.

What is astounding to a lot of us in South East Asia is the reluctance of the West in learning from our lessons. How many deaths and personal trauma experiences do people in general need to go through in order to learn from others?

There is a strong culture of individuality, and that is coupled with an extreme reluctance to just do what we're told, and what I mean by that is more about trust than Authority. Trust is low here, which is problematic for a scenario like this. Many of us did learn those lessons. For me personally when this all began, checking out what the world is doing seemed the natural thing to do. The US is also very insular, in…

I think it goes further than individuality, though. There's a pervasive selfishness that seems to run through our (American) culture. Many who do believe that COVID is a threat to others (say, to older people, or to immuno-compromised people) but do not believe that they themselves are in much danger will decide not to wear a mask because they don't think it matters to them if they do or not.

This is the thing that makes me saddest. It just seems like people in the US are unwilling to endure even a minor inconvenience if it will help someone else but not do anything for themselves.

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

#267

Post by beagle3 »

jonplackett wrote: post #140
rsj_hn wrote: 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…

I really don’t get why this is still considered a conundrum Lots of places have R hovering around 1. If it goes to 1.1 everything goes to shit, if it drops to 0.9. Everything will be fine. So even if masks reduce spread by a tiny amount, even 10% better. That could easily swing you below 1 and save the day.

The CDC study concluded 2% reduction. That’s in the range where harms need to be weighed too (e.g. masks that aren’t replaced often enough harbor bacteria themselves; there’s environmental costs, etc)

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

#268

Post by kelnos »

jasonlaramburu wrote: post #148
function_seven wrote: post #113

Earlier quoted context omitted.

> 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.

Or is it that people are taking the same amount of risks, but accidents that used to cause death are now "merely" causing head trauma?

(I don't know either way, just curious to know if this angle has been investigated.)

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

#269

Post by carlmr »

tgsovlerkhgsel wrote: post #129
carlmr wrote: post #121

Earlier quoted context omitted.

>It would be interesting to have a trial where everyone was wearing N95s, but we're not likely to see that. Bavaria and Austria had FFP2/KN95 only while the rest of Germany had the choice of surgical masks or FFP2, where almost everybody picked surgical masks (cheaper, not as annoying to wear). Now the rest of Germany switched to only FFP2 in public transport. So we do have some population studies. It didn't seem to…

Ventilation could also be a factor. You're more likely to open the window when the air outside is pleasant.

True, which is why it's even more important to get people to meet outside.

If you forbid inside and outside meetups, people will meet in secret, even closing their Windows so the neighbors don't snitch (this is Germany after all, the nation of snitches, historically :D).

A little bit of basic human psychology could have prevented some of these waves.

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

#270

Post by beagle3 »

dragonwriter wrote: post #254
nostrebored wrote: post #162

Earlier quoted context omitted.

Counterpoint: Miami

Miami-Dade County, FL has a little under half the cumulative confirmed cases as Los Angeles County, CA (500K vs. 1.2M) with a little over a quarter the population (2.7M vs. 10M), for a much higher per capita rate. So...how is it a counterpoint? (Case numbers from usafacts.org.)

I don’t know the details here, but in the Israel vs Sweden comparison, absolute numbers favor Israel (7000 vs 14000 dead) but age normalized are the same (Sweden has about twice as many >60), and in European normalized excess death measures from Oxford, Sweden is at 2% and Israel at 6%

Personally, I try to only use excess death figures, because case counts are not comparable due to local policies. E.g. once vaccination started, Israel categorically stopped testing vaccinees unless they show clear covid symptoms; whereas it demands weekly test from many unvaccinated even though they have no symptoms.

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