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Comment by red0point | Hacker News Reader

Well this is clearly stated in the paper.

* Only the visitors (cases A and C) sitting in the air flow path of case B were infected with COVID-19, while other visitors (V2, V3) closer to the infector for a longer period of time but in the absence of direct air flow did not become infected. In addition, the visitors sitting at tables with cases A and C (V1, V6, and V7) were not infected with COVID-19 because they faced away from the infector’s face. These findings strongly suggest that this outbreak occurred by droplet transmission exceeding a 2 m distance and excluded contact and fomite transmission. This transmission pattern is similar with the outbreak of a restaurant with air conditioning in Guangzhou, China.21 In this article, the authors concluded that the most likely transmission was done by droplet and also emphasized the direction of air flow.*

Also they analyzed the RNA to confirm linkage.

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This lines up with other studies I’ve seen which show that contact and fomite transmission do not significantly drive transmission (that means hand washing and surface disinfecting won’t make much difference).

Why would indoor dining be “safe”? Indoor anything is “unsafe”, as aerosolized transmission has been proven. Anything under a properly worn N95 doesn’t stop aerosols, and if anything will promote aerosols.

The idea that wearing a mask from the time you walk in the door to the time you sit down is somehow affecting outcomes is insane. People should know that walking into a restaurant carries some risk of infection and a mask isn’t going to change that.

1. https://www.acpjournals.org/doi/full/10.7326/M20-5008

Do you have evidence to back up your claim that properly worn EN14683 IIR masks are not sufficient?

How about because it says so on the label?

> Type I, I R, II and II R face masks are medical masks tested in the direction of exhalation (inside to outside) and take into account the efficiency of bacterial filtration. Surgical masks of this type stop the wearer from infecting the surrounding environment. They are not effective at protecting the wearer from airbourne diseases such as coronavirus.

> Type IIR face masks EN14683 are medical face masks made up of a 4 ply construction that prevents large particles from reaching the patient or working surfaces. Type IIR Face masks include a splash resistant layer to protect against blood and other bodily fluids. Type IIR face masks are tested in the direction of exhalation (inside to outside) and take into account the efficiency of bacterial filtration.

They are not designed or tested to stop inhaling large droplets, nor exhaling small droplets. There is no scientific evidence they prevent the transmission of COVID and they specifically disclaim as much.

However, properly worn FFP2, FFP3, N95 and other respirator masks are effective at protecting the wearer from viral transmission. That’s just not what most people are wearing outside a health care environment. And you can’t simply take them off when you sit down.

First hit on Google:

1. https://www.dental-nursing.co.uk/news/covid-19-a-guide-to-fa...

The key point is "Surgical masks of this type stop the wearer from infecting the surrounding environment"

Your mask protects me, my mask protects you.

Well forgive me but I was hoping for more than a first hit from Google and apparent common knowledge.

Since you mentioned having read studies about airborne transmission and aerosols, I was hoping you could point me to one where they examined the masks and found them to be significantly worse than FFP2.

Because in this study presented, only the people in the direct path facing the infected person were infected, not everyone, so wearing even EN14683 IIR masks could seem effective.

My guess, and this of many doctors in my area, is that EN14683IIR are, in fact, enough (if properly worn etc). If that is not true, I‘d like to know - from a reputable source.

The thing is specifically not designed to stop coronavirus, and specifically disclaims providing any protection against coronavirus. That’s not an editorial, that’s the written scientific standard for the medical device.

If you could get people to wear them without making people think they were a panacea then there wouldn’t be a problem (it would be a “can’t possibly hurt” situation). Unfortunately that’s not the equation that we’re faced with.

I’m sure EN14683 IIR is somewhat better than nothing, perhaps shifting the odds of infection somewhat lower depending on the circumstance. But if people slap one on and then feel they can’t be infected while standing in a room with people outside their household, that’s a mistake.

I think it’s blatantly obvious looking at flu vs. COVID numbers that it’s not that the precautions people are taking are not totally ineffective, they are just not nearly as effective as we need them to be against COVID.

They don't drive the transmissions the way they do for flu or some forms of common cold but I've seen estimates that 5% or so of infections come from fomites. It's still worth washing your hands when you come home and take off your mask since it's easy, but it's not going to make much of a dent in the R0.

Other sort of masks actually do make a dent in R0. A cloth or surgical mask doesn't provide the level of protection a N95 mask does but they do seem to provide a protection factor of 2 or 3. Nothing you could call safe but enough to reduce the R0 of the disease very significantly if everybody used them.

Where does this 2-3x factor come from? I just haven’t seen any proof of that.

From a macro perspective, masks did not stop the 2nd wave in Italy and France and their mask compliance was the highest in Europe. I don’t think you can claim Italy just didn’t mask hard enough.

Flu cases, by comparison, are down something like 99% year over year. So it’s not like I’m saying masks and hand washing don’t work. They appear to work extremely well for flu, they just obviously have failed to stop COVID.

If you look at how fearful some people are to even approach someone who isn’t wearing a mask, but then immediately feel safer when the mask goes on, it’s not clear to me a better approach wouldn’t have been “masks do not work, if you don’t want COVID then do not gather inside”.

Well, you can can put masks on dummies and see what fraction of aerosols of different sizes they stop, you can interview people after an outbreak and find out what protective measure they took and whether they get sick. You can look at which regions introduced mask mandates when and see what statistical result that seems to give on the number of covid cases. There have been an awful lot of studies on this topic over the course of the last 3/4 year and I'm also taking into account a study the WHO did after SARS-1 on mask effectiveness in Beijing. I wouldn't neccesarily have thought beforehand that fraction of particles stopped would line up neatly with reduction in chance of getting the disease but it seems to, at least roughly.

EDIT: Oh, and there are animal experiments where they put a layer of mask material between hamster cages and see if it prevents infections in the other cage.

” You can look at which regions introduced mask mandates when and see what statistical result that seems to give on the number of covid cases. There have been an awful lot of studies on this topic”

...all of which written in the spring, when cases were declining across the northern hemisphere. Subsequently, we’ve seen cases go up around the world, and it doesn’t seem to matter much if they have mask mandates, high self-reported mask compliance, or not.

This guy has amassed a huge collection of plots documenting the lack of impact of mask laws on outcomes:

https://mobile.twitter.com/ianmSC

Source on aerosolized transmission being proven? The discussion you're replying to is suggesting droplet transmission which are larger than aerosols and do not require an N95 mask.

Indoor dining is definitely a terrible idea, but if it's large droplets and not aerosols then you should be much better off with indoor activities where you can wear a mask.

I did cite a source, it discusses aerosol transmission and also the predominant method of infection (upper respiratory tract where the virus binds to ACE2 receptors) which is likely why surface contact spreading isn’t a huge problem.

That quote does nothing to disprove surface based infection though. Some people are better at not touching their faces than others.

True, however it makes sense if you look at the figure they provide, which shows airflow and infections:

https://jkms.org/ViewImage.php?Type=F&aid=694440&id=F3&afn=6...

If it were contact based, this would mean that at least one other in the restaurant must have contracted it that was outside of the airflow path. Since this not the case, the most likely thing is that transmission was with the airflow.

Why is it that you are so certain about this being surface based transmission?

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