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Comment by jjgreen | Hacker News Reader

On the face-masks, the majority of experts do think it's a good thing, but there is not really any solid evidence. The WHO June 5th statement on this:

At present, there is no direct evidence (from studies on COVID-19 and in healthy people in the community) on the effectiveness of universal masking of healthy people in the community to prevent infection with respiratory viruses, including COVID-19.

Indeed, interviewed on BBC Radio 4 last week, Professor Venki Ramakrishnan, president of the Royal Society (the UK "academy of science") declared that to ask for such evidence would be "methodological fetishism", we are expected, no demanded, to accept the opinions of experts.

So I'll stand with Feynman on this.

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There’s at least as much double-blind scientific trial based evidence of face mask effectiveness as there is the effectiveness of parachutes.

I've heard this a couple of times, it's a bit trite, a little anti-science, but worth some analysis. Suppose your analogy holds: which of mask-wearing and non-wearing is the parachute and which is the empty backpack? I ride the London underground regularly, masks are mandatory and 90-95% of people wear one. I'd say 20% of people let it drift down from their nose while they play on their phones, more than that are constantly adjusting it, touching their face with the hands that are also touching the seats and the hand-rails. Is this more or less dangerous than not wearing one at all? Are we really saying that this question is outside the realm of science?

Not at a community level. Only a droplet level. There's no measures on if stopping droplets compensates for the fact that people touch their face every 10 seconds due to wearing a mask. Numerous places with mask laws have skyrocketing case counts.

No there isn't. If there was, why is the British scientist demanding faith rather than presenting evidence for mask wearing? "Methodological fetishism" isn't a real thing, is it.

Here's the mask science reality: there is none. There have only been two studies that looked at whether masks stop a sick wearer infecting healthy people (the other way around to how masks are normally used), one was underpowered and the other concluded no impact. There's plenty of studies on whether masks stop a healthy person being infected by a sick person, but that's not how mask requirements are being justified at the moment.

If you think about it, designing a study to test this hypothesis wouldn't be possible. You'd have to ask for volunteers to specifically hang out in rooms around a sick person who was definitely shedding virus. But you aren't going to get permission to do that over and over again, probably you won't even be able to get volunteers. It's effectively unfalsifiable: exactly the kind of problem that makes for bad science.

It's possible that a simple mask can reduce transmission a bit, if someone is literally coughing phlegm into their mask. If they're not coughing up virus then how is a mask meant to work? The virus is too small to be directly blocked. It can only stop fairly large droplets.

>It can only stop fairly large droplets.

What is your basis for this statement?

If I wear a regular dust mask, without edge sealing, and glasses, my glasses fog up when I exhale. Seems to me suggestive evidence that anything at all deflects normally invisible breath that would travel outward onto the surroundings.

Well, that's pretty well known. There are different tiers of mask. This article looks at the evidence for them:

https://www.cidrap.umn.edu/news-perspective/2020/04/commenta...

Some kinds of masks can stop much finer grained objects than droplets, e.g. gas masks, but the kinds of masks people are actually wearing are just regular cloth masks and there's no evidence they accomplish anything and plenty of evidence they don't: the article goes into this.

It's logical: your glasses fog up exactly because the hot air is exiting the mask and travelling outwards, that's why it's hitting the cold glass of your glasses.

But it's not sufficient to merely deflect a small amount of air from each breath in a different direction. That's not permanently trapping infected air; obviously it can't be because otherwise CO2 saturated air would build up inside your mask and suffocate you. The air has to be able to circulate. The mask is meant to let air through whilst blocking ... well, whilst blocking what? Virus particles? They're far too small. Water droplets that contain virus? Maybe, but only if you're actually spreading water droplets around and if you're asymptomatic then clearly you're not. Yet everyone is being forced to wear masks even if they're visibly healthy, on the basis that "you might be infected without realising it". The science behind this is garbled nonsense, being pushed on people because something must be done, this is something, therefore it must be done.

Stopping stuff travelling out is a different matter.

The other thing that's being missed is even for proper masks there are time limits to their effectiveness. That doesn't matter so much for health care professionals who should be frequently replacing the masks, but it is relevant to members of the public walking around.

Either they're keeping the mask on all day and it stops being useful after an hour, or they're taking it off and putting it on as they go in and out of shops.

https://www.ijic.info/article/download/10788/7862/

> This study was conducted to check the efficacy of face masks in limiting bacterial dispersal when worn continuously in Operation Theater. A comparison was done to find out difference between fabric and two ply disposable masks. The first sample was collected prior to wearing the mask, using cough plate method holding a blood agar plate approximately 10 -12 centimeters away from the mouth. The personnel were asked to produce “ahh” phonation. Participants were then asked to don the face mask, continue routine work and report to the study center located inside the theater for further sample collections at designated intervals of 30, 60, 90, 120 and 150 minutes after wearing the fabric mask made of cotton. The study was replicated on immediate next day using two ply disposable mask keeping all the other conditions and personnel exactly the same. Bacterial counts before wearing the mask were 5.36±4.38 and 5.7±2.99 on day 1 and day 2 of study. Bacterial counts were 0.96±1.06 (P<0.001) and 0.7±0.87 (P<0.001) at 30 min; 2.33±1.42 (P<0.001) and 2.36±1.03 (P<0.001) at 60 min; 3.23±1.54 (P=0.007) and 4.16±1.78 (P=0.011) at 90 min; 5.63±4.02 (P=0.67) and 4.9±1.98 (P=0.161) at 120 min and 7.03±4.45 (P=0.019) and 5.6±2.21 (P=0.951) at 150min respectively for fabric and two ply disposable mask. Counts were near pre-wear level in about two hours irrespective of the type of mask. There was no significant difference between cotton fabric and two ply disposable masks. Face masks significantly decreased bacterial dispersal initially but became almost ineffective after two hours of use.

There is a key part of that phrase "of healthy people". The problem here is that lots of people dont realize they are sick, or are in the earily stage of the sickness with low symptoms yet still infectious. The evidence for this position increases daily.

I agree with you here that, that is definitely an issue. One should never be ridiculed or looked down upon when asked for scientific evidence. But I guess that is a completely different subject of "scientific elitism" or "scientist elitism",

Not that is of any help but the government in Denmark has done sort of the same. If you question their policies and responses to COVID they say “It’s based on advice on scientists and professionals”. You ask what professionals and science for long enough they say well it was a political decision. And this circle go around in till someone gets tired

On the topic of masks, unfortunately people are forgetting that initial spread of SARS-COV-2 was through the eyes.

We will learn a lot from the post mortem of this pandemic...

How you get infected is irrelevant unless you are spending your time in a COVID-19 hospital ward. The question is how you avoid infecting others, in the world as it exists, where most people are not infected but you might be.

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