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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

#81
post #63

Earlier quoted context omitted.

Unfortunately, a few of my friends fell victim to the Qanon conspiracy bandwagon and the fact that mask pore size is wider than the virus was heavily circulated as a reason for mask ineffectiveness.

Everyone is having assumptions about these observations. The conclusions might not be always right, but at least the observation is real. And when you observe that mask mandating states don’t do significantly better than mask-free states, then a curious mind rightfully starts pondering. No need to unterstand conspiracy theories (a difficult topic) to understand that science isn’t getting it right yet.

> And when you observe that mask mandating states don’t do significantly better than mask-free states, then a curious mind rightfully starts pondering.

If this is true, which I haven't confirmed, wouldn't that say more about the effectiveness of political policy rather than about masks themselves? When we have seen throughout the pandemic that healthcare workers have a dramatically lower rate of infection compared to the general population, despite having more direct contact with infected populations, it is clear to the that proper precautions including protective equipment (principally masks, for a respiratory disease) can impede COVID transmission heavily. With that being the case, the question becomes: has mask policy been effective in getting enough people to wear masks properly and consistently, in states where it is mandated?

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

#82

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?

Probably not. Most things like this are like this. There may indeed be some underlying proof, but they either can't or won't show it to you-if it exists. It is more likely that it does not. They start with their conclusion. They rarely commence an empirical study, because that might prove their prepared conclusion wrong! A model, which can be used in place of reality, is not reality, and never will be. GIGO. The model was tailored to match their wanted results, or more likely they made a bad model and tweaked it to gain desired results. This does not mean that masks are bad-it just means that the methods used are generally false. Properly gained empirical evidence should be used, and it even should not be trusted if it points to you doing something stupid-like wearing a tissue on your face all day.

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

#83

N95/FFP2 seem to be very effective. I wish the media and government would have spent more time in educating people in things like how N95 masks work and that it isn't like a coffee filter. Even thought the pores are larger than a virus the masks are statically charged causes smaller things to get trapped. Many people don't know this but probably had an interaction with static electricity sometime in school and would…

I get where you are coming from but something I've learned from this pandemic is that "wear a mask" is too complex and burdensome for a significant proportion of people in the west...

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

#84

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?

No you didn't miss anything - most people upvoting this didn't read anything more than the title.

So true.

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

#85

The VAST majority of mask wearing I have seen in California has been average cloth-covers. I have only seen a handful of people out of thousands actually wearing N95 masks, so perhaps N95 is highly effective at stopping viruses, but I see basically nobody wearing that. Stores, offices, buildings, all are completely fine with you wearing a bandana over your face. There is effectively no point in even mandating mask la…

I've never seen anyone wearing a coffee filter over their face. What are you talking about?

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

#86
post #60

N95/FFP2 seem to be very effective. I wish the media and government would have spent more time in educating people in things like how N95 masks work and that it isn't like a coffee filter. Even thought the pores are larger than a virus the masks are statically charged causes smaller things to get trapped. Many people don't know this but probably had an interaction with static electricity sometime in school and would…

I don't think people need to know how they work. They just need to know that those are what doctors wear and that they are very, very effective. And much better than a mask you make from ad hoc materials. Once N95 masks became readily available and cheap, it was (and is) mysterious why people weren't being told to wear them to protect themselves instead of wearing whatever was at hand to sort of protect themselves an…

Last I checked in Canada, N95 masks are still about 3$ a pop for disposable, single use masks from industrial distributors. Pre pandemic, we bought 3M 8210s for about 15 cents in boxes of 160. I wouldn't call the current situation available and cheap.

Oh, and if you thought surgical masks were mildly uncomfortable, N95s are an order of magnitude worst. They pretty much need a perfect seal with your face and the 3Ms use a really tight rubber band to achieve that. 2 bands, actually.

I currently work on site and wear surgical masks all day, it's fine. Not sure I would want to do the same if it was N95s.

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

#87

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…

There is no evidence that inoculation with sub-viable numbers of virions works at all as a kind of vaccination. It's an interesting hypothesis but no one has done the human challenge trials necessary to test it.

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

#88
I don't know. We had some of the highest mask wearing percentages in the country here in Southern California, yet some of the highest infection rates in the world. Something isn't adding up here. I'm guessing if everyone had N95 masks, we would have seen lower numbers however. I don't think the average cloth masks that people are wearing are very effective.

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

#89

Earlier quoted context omitted.

A big part of why they are annoying and uncomfortable is the lack of one-way valves to make it easier to breath in them. In industry, when you actually need to wear a mask/respirator, they almost always have valves. Unfortunately, we got stuck on the "wear masks to protect others" narrative, and people who actually were at risk were prevented from wearing much more effective, much more comfortable, masks that would a…

I don't think it is an unfortunate narrative. two people wearing masks without valves is twice the reduction in likelihood that either one gives the other covid. If someone does have covid the mask without the valve will greatly reduce the concentration of virus particles in the air around them. I think that is working as intended!

Masks that aren't worn correctly tend to have very low efficiencies, because the air just bypasses the mask at the edges. Depends on many factors like the type, how hard you are breathing, etc. But filtering just 20% of the air breathed in is quite possible. And let's face it, people intentionally wear them incorrectly all the time because they suck to wear.

If you and I both have 50% filtration, that's the equivalent of 75% filtration. For the person who is vulnerable, that is much less effective than just wearing a 95% minimum filtration valved N95 mask/respirator properly.

It's just ridiculous that an elderly man on a flight, sitting next to a healthy 15 year old more likely to be killed by a flu infection(1), will be told to take off his valved N95 respirator here in Canada, to protect that 15 year old. I have friends who have seen this happen first hand.

1) https://www.cdc.gov/flu/symptoms/flu-vs-covid19.htm

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

#90

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?

The paper is fine, the title is clickbait.
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