conventional wisdom

[calimac]

Here's what used to be the conventional wisdom about masks in the pandemic:

1. Any mask that covers your nose and mouth is much better than no mask.

2. A cloth mask is better at preventing you from breathing out virus (if you have it) than at keeping you from breathing it in, but it helps enough with the latter to be worth the trouble.

3. An N95 mask does not offer much additional protection unless you fit it properly.

3a. And even people who wear N95s regularly, like health care workers, mostly do not know how to fit the mask properly.

4. If you do fit the mask properly, it will be so tight over your nose and mouth that you'll have trouble breathing, especially if you're exerting yourself. Another reason not to wear one.

4a. If you have a beard, forget it. The N95 will not have a tight enough fit.

Here's the current conventional wisdom about masks:

1. Cloth masks are almost completely useless. They're "mask theater."

2. An N95 is the minimum necessary prevention. Nothing about the difficulty of proper fitting. Just make sure you have the straps around your head in the correct manner.

What I want to know is, why did the conventional wisdom change? That it has changed, and that there are official pronouncements to back this up, is amply documented. That's not what I'm looking for. I want to know why the change.

I can think of some possible reasons:

1. The increased transmissibility of the omicron variant has changed the dynamics of risk.

2. New studies have overturned what we thought we knew.

3. The old thinking was folk-wisdom to begin with, and was never valid.

4. The new thinking is the result of hysteria or improper influence (like the reduction of isolation periods from 10 to 5 days) and isn't valid.

But which, if any, of these is true has not been discussed anywhere that I've seen it. Indeed, the old wisdom seems to have disappeared in enlightened circles as if it never existed at all. What's going on here?

Comments

[voidampersand]

There are a lot of cheesy cloth masks. That doesn't mean cloth masks can't be good — my sister makes cloth masks from proper materials, following WHO and CDC guidelines. Just that a lot of cloth masks we see aren't that good. I'm thinking of a friend with a cloth mask that doesn't fit right and it's always falling down off his nose. If it was his pants always falling down like that, he'd do something about it.

The increased transmissibility of omicron compared to other variants seems like a legitimate reason for using masks with better filtration.

Another change from the beginning of the pandemic is now it's easy to find good, inexpensive KN95 masks that fit well.

Whether a mask fits over a beard really depends on the shape and thickness of the beard. The rules for fitting N95 masks were bureaucratic and meant for a small community of medical professionals who could be held to very strict standards. Now the masks are needed in the larger population, what matters is what works.

So, multiple factors. And science should change as we learn more, otherwise it's dogma, not science.

[calimac]

Criticism of poorly-fitting cloth masks (and pathetic mask-substitutes, like bandannas) long predates the change in conventional wisdom. That's not what this is about. They say cloth masks period, and imply (but don't state outright) that reinforcing them is not much help. Sounds like you're guessing at the specific reasons for this specific change, even as I am.

[petrea_mitchell]

I'm not sure where this "conventional wisdom" is coming from; medical experts in the stories I read are still saying that any mask is better than no mask, though there is more emphasis on the need for a good fit and the necessity of at least 2 layers if you're sticking with cloth.

The general drift of health recommendations since early 2020 has been governed by improved scientific understanding, like the change from treating the virus as primarily transmitted by infected surfaces to primarily transmitted by aerosols. The sudden move to everyone needing booster shots and stronger nudges to upgrade your mask come from omicron being possibly as transmissible as measles.

If you're vaccinated and boosted, then you're still well-protected against severe illness. But the reduction in risk of hospitalization is outweighed by the much, much, faster spread. Thus the tone of mild panic as health experts contemplate hospitals being once again in danger of being overwhelmed, even in highly vaccinated areas.

[calimac]

Thank you, but I have no trouble understanding the other changes in recommendation. This is the one that's coming without explanation that I can see.

[steepholm]

I think conventional wisdom may be a bit different in the UK. In particular, N95 masks are not at all popular here, partly on what I suppose one might call cultural grounds: i.e. they are good at protecting you from other people, but don't protect other people from you - whereas a lot of the rhetoric here is framed in terms of not endangering others.

[calimac]

Thank you, but this leaves me more puzzled than before I read it.

N95 are indeed supposed to be better than other masks at protecting you from other people, but you write that they "don't protect other people from you." How can they be less good at that than cloth masks? Or do you just mean that they're no better at it than other masks, so that's not a reason to seek them out?

The rhetoric around the old conventional wisdom was about not endangering others. See point 2 in my post, that cloth masks were supposed to be inefficient at filtering incoming air, though a lot better than nothing, but their primary virtue was that they preventing you from spewing. But see LSAnderson's comment below that they're now supposed to be useless at that.

I haven't been so baffled about anything that's supposed to be perfectly obvious since the justifications for invading Iraq.

[steepholm]

I'm speaking here not as a spew analyst, only as a conveyor of what I see on the internet (you may reasonably feel this distinction is not a big one). But my impression is that the N95 is great at filtering incoming air, but because of the valve it lets whatever nasties you breathe out into the atmosphere as is. This may be totally wrong.

[calimac]

Valves? N95s in the US don't have valves. Never mind conventional wisdom in this case, the official wisdom throughout the pandemic has been strong and consistent: do not wear a mask with a valve, period. And you've identified the reason for this.

[steepholm]

In that case it's entirely possible that I'm conflating two different things, or that other people are.

[steepholm]

Ah, it seems some do, some don't.

Oh

[lsanderson]

I read somewhere that a main advantage of N95 masks is preventing you from spewing a cloud of virus in front of you no matter how poorly the mask fits. Cloth masks pretty much fail at this. N95 are also better filtering, but that depends on fit.

I think new studies, but I'm unsure where all they have been published.

Kevin Drum has a summary here: https://jabberwocking.com/heres-a-quick-look-at-the-evidence-about-mask-wearing/

Re: Oh

[calimac]

Thank you, I guess, for you have increased and focused my puzzlement.

I had forgotten about it specifically, but the Kevin Drum article you link to was one of the main sources for my impression that the conventional wisdom had changed and that cloth masks are useless. But Drum doesn't say anything about why it's changed. Hence my puzzlement.

I am further puzzled by your statement that cloth masks pretty much fail at preventing you from spewing a cloud of virus. 1) How can they fail at this? They're a mask in front of your face! 2) If they do fail, that's a purely mechanical issue, so how could this not have been discovered at the outset; why did it take "new studies" to bring it up?

Re: Oh -- TMI

[lsanderson]

I assume cloth masks are not filtering anywhere near the size or capacity of N95 masks:

"4. How do N95 masks block SARS-CoV-2?
N95 masks are designed to remove more than 95% of all particles that are at least 0.3 microns (µm) in diameter. In fact, measurements of the particle filtration efficiency of N95 masks show that they are capable of filtering ≈99.8% of particles with a diameter of ≈0.1 μm (Rengasamy et al., 2017). SARS-CoV-2 is an enveloped virus ≈0.1 μm in diameter, so N95 masks are capable of filtering most free virions, but they do more than that. How so? Viruses are often transmitted through respiratory droplets produced by coughing and sneezing. Respiratory droplets are usually divided into two size bins, large droplets (>5 μm in diameter) that fall rapidly to the ground and are thus transmitted only over short distances, and small droplets (≤5 μm in diameter). Small droplets can evaporate into 'droplet nuclei', remain suspended in air for significant periods of time and could be inhaled. Some viruses, such as measles, can be transmitted by droplet nuclei (Tellier et al., 2019). Larger droplets are also known to transmit viruses, usually by settling onto surfaces that are touched and transported by hands onto mucosal membranes such as the eyes, nose and mouth (CDC, 2020). The characteristic diameter of large droplets produced by sneezing is ~100 μm (Han et al., 2013), while the diameter of droplet nuclei produced by coughing is on the order of ~1 μm (Yang et al., 2007). At present, it is unclear whether surfaces or air are the dominant mode of SARS-CoV-2 transmission, but N95 masks should provide some protection against both (Jefferson et al., 2009; Leung et al., 2020).'"

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7224694/

For filtration efficiency of cloth masks: https://pubs.acs.org/doi/10.1021/acsnano.0c05025 -- it's kind of like you can hold a cheese grater in front of your face and it will stop some particles, but not many.

My guess is that no one on this side of the large pond cared enough after the Spanish Flu to do the basic research. Asia has been the only place half in love with cloth masks both because of air pollution and various swine and bird flus.

Re: Oh -- TMI

[calimac]

Nobody ever denied that N95s are more efficient than cloth masks, at least if the N95 is fitted properly. If it isn't, it has the same blowout on the side as any other mask does, but in the new wisdom that fact is being ignored.

The only part of the second article I could understand was that multiple layers are better than a single layer. But how much better, the new anti-cloth consensus doesn't say: the implication is that it isn't better enough to make a difference.

You seem to be saying that health officials and general commentators spent nearly two years urgently promoting cloth masks without anyone ever having bothered to check as to whether they work at all. I am skeptical that this could be true. Especially because the subject of the efficiency of cloth masks had been investigated in the context of smoky air during the fire seasons of the past several years.