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Comment by Mr_P | Hacker News Reader

Masks are effective at stopping people from unintentionally infecting others.

See: https://www.nytimes.com/2020/04/10/well/live/coronavirus-fac...

"Even a simple mask is very effective at trapping droplets from your coughs and sneezes. A recent study published in Nature from the University of Hong Kong and the University of Maryland asked 111 people, infected with various viral illnesses (influenza, rhinovirus and a more-mild coronavirus), to exhale into a giant funnel. Sometimes their noses and mouths weren’t covered; other times they used a simple, not-particularly-well-fitted mask.

Without the masks, the infected people exhaled contagious droplets and aerosols, tiny particles that linger in the air, about 30 percent of the time they were tested. When the infected patients wore a mask, it blocked nearly 100 percent of viral droplets and some of the aerosol particles."

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But in 1918 they were using specifically gauze, presumably because it's easier to breathe through, or maybe just because it seems medical-y.

The study in the NYT article is using non-woven paper masks, which act a decent barrier to ballistic particles. Gauze would be way less effective than even loose woven fabric at stoping the 5um particles they're measuring. Like the paper masks, it would be completely ineffective at stopping the influenza-carrying aerosols.

"nearly 100%" is a pretty big misstatement of the study as well, while it showed a statistically significant difference between the groups, so much of the no-mask control group recorded 0 virus load from droplets that the size of the effect can't be meaningfully quantified

But see this research, which found masks didn't help prevent covid-19 from leaving infected people.

https://annals.org/aim/fullarticle/2764367/effectiveness-sur...

If people are going to wear masks we need to make sure that they don't touch the mask or their face, or that they wash their hands immediately after doing so.

Interesting, they state the conclusion that "both surgical and cotton masks seem to be ineffective in preventing the dissemination of SARS–CoV-2 from the coughs of patients with COVID-19 to the environment"

But they also say this: "The median viral loads after coughs without a mask, with a surgical mask, and with a cotton mask were 2.56 log copies/mL, 2.42 log copies/mL, and 1.85 log copies/mL, respectively."

That seems like a significant reduction in transmitted viral load? I would think that masks can have a positive impact even if they aren't perfect filters. If you look at their table of data, the reduction trend is consistent across their tests. But between the small number of patients(4) and samples, and the number of Petri dishes that came back as 'Not Detected', it seems like a pretty low powered study. :-/

They are also explicitly testing coughs. I wonder about the effects on filtering droplets generated from normal breathing and talking.

> I would think that masks can have a positive impact even if they aren't perfect filters.

That is when behavior comes in. If people are more likely to ignore social distancing if they wear a mask then you might get the opposite effect, as social distancing is seen as better protective measure than masks.

This is one of the reasons why the health department in my nation only recommend masks for risk groups, like if you are working with elderly people.

This is a completely speculative conjecture known as risk compensation (https://en.wikipedia.org/wiki/Risk_compensation). It's often brought up in opposition of mandatory safety measures (quite prominently around seat belt legislation in the 1970s), but AFAIK it's never been shown to be numerically significant.

It was suspect with bicycle helmets. But alternative hypothesis is that if helmets are mandated, people dont use bikes as much for transportation or causual pleasure rides, biking only for serious sport (making incidents go up per ride).

Risk compensation, as in the idea that people are more conservative when they feel more at risk, is pretty well founded. It's risk homeostasis, namely the idea that people will voluntarily increase their risk until a target level is reached, that's controversial: https://en.wikipedia.org/wiki/Risk_compensation#Risk_homeost...

I recall reading some interesting research on this when it comes to playgrounds: these days unforgiving concrete is being replaced with bouncy rubber, and the compensation/homeostasis theory is that kids are playing in riskier ways because small tumbles don't hurt them any more.

The people responsible at the health department could be wrong, as they are just employees, and could be misinformed/ill-trained. It is a speculative theory, and the official statement empathize that the singular most important thing people should do is is to stay at home if they are sick. The medical benefits of mask for people without symptoms is not clear (but I would be interesting to read research if someone can link that), and there is a supply demand right now to get mask to those groups that really need them.

It is not a black and white issue of seat belt where there is ample proven evidence that in basically any car crash a seat belt is better than no seat belt. There is no shortage of seat belts, nor has there ever been one. The focus of car safety has also primarily focused on speed, where the survivable limit goes up if the driver has a seat belt, but even that higher limit is still much lower than the speed of many drivers. Thus the message there is to inform drivers the importance of both the benefit of seat belts, but also the critical message that speed more or less determine if a person is going to live or die. Even if people would risk compensate and go from the survivable speed without seat belt and increase their speed to survivable speed with seat belt, it would still be lower than what many people already drive their cars at. The worst case scenario of seat belts would thus be an improvement. We can not say the same thing about social distancing, where going out sick with a mask on is still a very bad idea.

Thus the recommendation from the health department is right now that masks should go to those in risk groups and people who are sick should stay home. If research later show that people without symptoms reduces risk of infecting others by wearing a medical mask, and the supply of masks increases, then they will likely change their recommendation based on the changed situation and facts.

(Small meta comment, but it is interesting how skeptical people are of the medical department that is responsible for handling the pandemic. It is true that critical questioning any government recommendation is useful, but maybe a bit more open minded discussion would be better).

Indeed, the actual numerical results in the article table shows that masks are very effective, so it's puzzling where their narrative conclusions came from.

A log-reduction of around 0.5 isn't much. "very effective" would be like 3-4 which even this n=4 study is enough to rule out

0.5 log-load reduction is a 66% decrease. A 1.5 reduction is 96%, which is N95 standard. Starting from 2.56, a log reduction of 3-4 is impossible.

In any case, the large number of NDs (not detected) everywhere in the table, but especially inside the masks after the patient just coughed in them (which the authors struggle to explain), makes this entire experiment very suspect. (Just look at the reported results for patient 4, which make no sense at all!)

No offence you might want to brush up on your Maths and how log scales work.

No offense but you should do a better job at explaining whats wrong instead of telling someone to brush up on math.

Lower numbers may not have enough of an effect on transmission rates.

The problem is that 99%+ of viruses are either harmless or symbiotic so any method that cant tell harmful from harmless might not give valid results.

> 99%+ of viruses are either harmless or symbiotic

There is no such thing as a symbiotic virus.

Placental mammals need certain endogenous retroviruses in order to reproduce.

The choice is not between "completely useless" and "100% effective". That is false dichotomy. Things like masks can be 70% effective which is already making situation better, although not perfect.

I will rephrase you:

> If people are going not to wear masks we need to make sure that they don't touch their face or that they wash their hands immediately after being in contact with anything anything would be in contact too.

Same thing, the washing hands and keeping distance is stuff you are supposed to whether you wear mask or not. Mask is not putting you into additional danger as far as I know. We don't need to put special additional conditions on masks wearing.

> The choice is not between "completely useless" and "100% effective". That is false dichotomy. Things like masks can be 70% effective which is already making situation better, although not perfect.

Sure. Masks have a plausible mechanism of action. Now show me using good evidence that masks i) don't increase risk and ii) decrease risk.

At the moment the mechanism for increased risk is as plausible as the mechanism for decreased risk. Masks are uncomfortable and people need to adjust them during the day -- this is an increase in face touching, and masks are by definition contaminated.

> the washing hands and keeping distance is stuff you are supposed to whether you wear mask or not

The only point of wearing masks is when you cannot socially distance yourself from other people. That's why masks are being pushed so hard now -- to end the lockdowns and get people back into work.

Is the argument you're making that we're trying to compare:

1) masks decrease the spread of disease by decreasing your germy breath from spreading and by decreasing you from breathing someone else's germy breath

2) masks increase the spread of disease by causing you to touch your mask with your germy hand, which increases the chance that germs can spread from your hand to your mouth?

and that the benefits of (1) do not outweigh the downsides of (2)?

I think that could be easily proven by showing that it's very unlikely to spread germs through the air but very likely to spread germs via touch.

For 2. you'd either be contaminated directly from those particles landing on your face or by you touching your face directly, anyway, so I'd consider 2. to not be a strong argument against masks, anyway.

2) Being related to specific mask wearing seems implausible to me.

One of the fun highlights of this disease has been the official advice to not touch your face, followed immediately by the realization that we all touch our faces a lot. The idea that masks specifically cause you to touch your face more than we already are doesn’t pass the sniff test.

Also, if you are having to touch your face a lot while wearing a mask, you have the wrong mask. I wear one to the grocery store and after an initial adjustment I don't usually have to touch it again.

> At the moment the mechanism for increased risk is as plausible as the mechanism for decreased risk.

It does not seem to me. There is like no study that shows masks increase risk of spreading infection and I have seen multiple that show it takes it at least somehow down. (I am lazy to search it down again. In pretty much all these discussions someone linked.)

> Masks are uncomfortable and people need to adjust them during the day -- this is an increase in face touching, and masks are by definition contaminated.

Even if this was true, you are still less likely to infect others if you are asymptomatic. It is not just about you. And as someone who was wearing mask for multiple weeks (they were mandated here), it is not some kind of horrible uncomfortable.

> The only point of wearing masks is when you cannot socially distance yourself from other people. That's why masks are being pushed so hard now -- to end the lockdowns and get people back into work.

You are also meeting people in stores, in public transport, when walking on the street anywhere. Even in lockdown, people still need to eat. Sure you don't need mask when you are alone in the forrest. You dont need to wash hands there either and can touch your face as much as you like (at least not due to coronavirus).

When I am alone in my house with supplies, I dont need to do anything special and I can touch my face as much as I want. All other measures apply only when you are in space shared with other people.

> Masks are uncomfortable and people need to adjust them during the day -- this is an increase in face touching, and masks are by definition contaminated.

Which is part of why the anti-mask narrative has been so harmful. Recommended mask wearing should have started back in early March so that everyone could gain experience before the virus was so widespread - knowing how to adjust their mask so it was comfortable, becoming used to it and not fidgeting, and learning how to incorporate mask donning/doffing into their overall hygiene procedures.

It also would have been nice to get data on the growth of cases with mask usage but without shutdown. Now we're left with the decision of whether we're ready for cases to start growing at some unknown faster rate.

I really dislike this all or nothing attitude. It poses so many requirements that people are going to give up on it. It is the same as all the bullshit that flew around in Feb. regarding how you shouldn't be wearing a mask and that you might increase your risk of infection by wearing a mask. Its all bullshit. Yes, you should not be hoarding a supply of n95 masks because these need to go to healthcare workers. But yes you should be wearing something, even a cloth mask if you are going out to a grocery store or anywhere in public with other people around. Is it going to stop it completely? No, but I think we have enough of an idea about the science that the viral load plays into the chances of getting infected.

So why don't we try to do our best and wear masks of any type that we can, and prevent the spread no matter how small? I am just sad people like you have really hurt countries. I know in America we should have been pushing the agenda that we should be wearing masks outside, we should not be hoarding medical masks, we should be washing our hands, and even more importantly we should be taking body temps before entering buildings.

The person you are replying to is talking specifically about Influenza which isn't spread as widely through droplets, while COVID-19 is spread this way almost exclusively.

"Most experts think that flu viruses spread mainly by droplets..." (https://www.cdc.gov/flu/about/disease/spread.htm)

Mainly /= exclusively. COVID as far as we know are spread exclusively through droplets. Influenza can be aerosolized https://www.cdc.gov/niosh/topics/flu/transmission.html

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