13 ms·

Indeed this is the money paragraph: "The effectiveness of masks, however, is still under debate. Compared to N95/FFP2 respirators which have very low particle

by rsj_hn 5y ago

Indeed this is the money paragraph: "The effectiveness of masks, however, is still under debate. Compared to N95/FFP2 respirators which have very low particle penetration rates (around ~5%), surgical and similar masks exhibit higher and more variable penetration rates (around ~30-70%) (2, 3). Given the large number of particles emitted upon respiration and especially upon sneezing or coughing (4), the number of respiratory particles that may penetrate masks is substantial, which is one of the main reasons leading to doubts about their efficacy in preventing infections. Moreover, randomized clinical trials show inconsistent or inconclusive results, with some studies reporting only a marginal benefit or no effect of mask use (5, 6). Thus, surgical and similar masks are often considered to be ineffective. On the other hand, observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease 2019 (COVID-19) (7–9). So how to explain these contrasting results and apparent inconsistencies? Here, we develop a quantitative model of airborne virus exposure that can explain these contrasting results and provide a basis for quantifying the efficacy of face masks. " So they are left with a conundrum that places which use surgical masks seem to be better off, whereas randomized control studies of surgical masks show little to no benefit. This is what they try to explain with a mathematical model.

BugsJustFindMe 5y ago
The mistake that many people make, and that I think you're implicitly making here too, is this notion of "controlled study". If the study denies the result seen time and again in real life, perhaps the study isn't studying correctly.
- colonelanguz 5y ago
  How many agains makes the study wrong
- bawolff 5y ago
  If we fully understood what was happening in real life, we wouldn't need studies.
function_seven 5y ago
> On the other hand, "observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease 2019 (COVID-19) (7–9)." So how to explain these contrasting results and apparent inconsistencies? My hypothesis regarding surgical mask prevalence and how it correlates with better virus control: People who wear masks--however effective they may be--also behave in other ways to limit the spread. They minimize time spent in public indoor spaces, they keep distance from other people, they're more likely to self-quarantine if a family member is sick, etc. The mask-wearing prevalence is a proxy for how serious the wearer takes Covid as a threat.
- jasonlaramburu 5y ago
  It’s worth also considering the case of ski helmets. Since these have became common on the slopes head trauma has actually increased because wearers take more risks.
  - swader999 5y ago
    Probably related to the uptake in snow boarding.
  - lostlogin 5y ago
    I had previously read that WW1 saw an increase in head injuries when helmets were used, due to victims surviving previously fatal injuries. However on searching it doesn't seem that clear-cut.
  - AuryGlenz 5y ago
    I definitely noticed a change in behavior at stores and at weddings I photographed once the mask mandate happened. Before it happened? Small backyard ceremonies with just families. In stores people straight up avoided being close to others. After? Normal, but with masks.
  - function_seven 5y ago
    Yeah, or the idea that maybe helmets in gridiron football increase CTE. I see the possibility, but my own anecdotal experience with mask wearers and non-wearers jives with the other correlation: that non-wearers generally didn’t take the pandemic seriously. The people that I know who shunned masks also ignored the COVID threat in other ways: Large gatherings, vacations to another state to escape lockdown restrictions, etc. Whereas my religiously-masked friends were basically isolated last year. And because I have several such anecdotes, I now have data :)
wrycoder 5y ago
I suspect that in locations with a higher prevalence of masking the population is generally more vigilant: more hand washing, more social distance, stay at home when ill, avoid obviously ill people, and so on. May be a case of correlation, not causation. It would be interesting to have a trial where everyone was wearing N95s, but we're not likely to see that.
- carlmr 5y ago
  >It would be interesting to have a trial where everyone was wearing N95s, but we're not likely to see that. Bavaria and Austria had FFP2/KN95 only while the rest of Germany had the choice of surgical masks or FFP2, where almost everybody picked surgical masks (cheaper, not as annoying to wear). Now the rest of Germany switched to only FFP2 in public transport. So we do have some population studies. It didn't seem to make much of a difference. I'd say the factor overwhelming almost every other measure is the weather. More people outside means dropping case numbers. More people at home means rising case numbers. It's been true for influenza and cold, and it's still holding up for Corona. If any measure would make sense it would be to allow people to meet outside while forbidding it at home. They only forbade at home without allowing outside meetups, which made home parties more likely.
  - tgsovlerkhgsel 5y ago
    Ventilation could also be a factor. You're more likely to open the window when the air outside is pleasant.
    - carlmr 5y ago
      True, which is why it's even more important to get people to meet outside. If you forbid inside and outside meetups, people will meet in secret, even closing their Windows so the neighbors don't snitch (this is Germany after all, the nation of snitches, historically :D). A little bit of basic human psychology could have prevented some of these waves.
- asabjorn 5y ago
caddemon 5y ago
The RCTs I have seen with basic surgical masks also seem to focus only on protection of the wearer, whereas on a societal level wearing even a shitty mask may be helping to prevent spread by presymptomatic people. I think it is unlikely the positive outcomes in mask wearing communities are purely due to confounders, although of course they probably also play a role.
- splithalf 5y ago
  I suspect mask wearing increases social distancing. That would explain much of the data but satisfy neither political party.
  - caddemon 5y ago
    I'm not sure about that honestly. At the extreme there's definitely COVID deniers who followed no precautions, but IME most "normal" people I know felt more comfortable spending time indoors with masks than they would have otherwise. And 6 feet is really not enough spacing in many indoor environments. With things like elevators the other person could be gone and you could still be exposing yourself. There is also precedence for some of these statistics with Asian countries during the SARS pandemic, and in these places rule following is generally much better. And with a smaller sample size there are some case studies from restaurant transmission. Staff seem to get infected less frequently than other diners, even though they are in the space for longer. There are a few possible explanations, but the fact that staff don't take their masks off is a pretty compelling one.
    - __blockcipher__ 5y ago
      > Staff seem to get infected less frequently than other diners, even though they are in the space for longer. There are a few possible explanations, but the fact that staff don't take their masks off is a pretty compelling one. IMO that’s the least compelling reason. One big one would be the staff having way more contacts and thus higher exposure to the other circulating hCoVs as well as SARS-2 itself. The evidence for face masks is weak at best. In my opinion they don’t even make sense theoretically unless you pretend that droplet transmission is the dominant transmission mode, which is completely unproven yet widely believed dogma (go figure)
tgsovlerkhgsel 5y ago
What I don't understand... the UK was already doing challenge studies (intentionally infecting consenting volunteers). Why didn't they make one with masks? Really can't be that hard to take a known infected person, sit them on a chair, arrange 100 people around them for a few hours with masks applied in a checkerboard pattern, and observe the results. This is usually out of question for ethical reasons, but they already decided that that wasn't an obstacle, so why not (also) do a study on this? (Or rather, arrange 10x 10 people, in 5 rounds putting a mask on the infected person.)
- mattzito 5y ago
  The challenge studies they’re doing involve infecting people with measure doses of the virus. An infected person may or may not be shedding at that particular moment. Once they’ve established the MED to infect someone, they could potentially do a study with aerosols and masks, but even then, trying to simulate the right airflow and volume of viral particles is probably too difficult to be practical.
_Nat_ 5y ago
tl;dr- There wasn't really a conundrum to explain related to mask-effectiveness at different levels. Rather, it's more like a lack of good data, as prior studies being cited were ridiculously weak. --- This seems like a largely helpful characterization. However: > So they are left with a conundrum that places which use surgical masks seem to be better off, whereas randomized control studies of surgical masks show little to no benefit. This is what they try to explain with a mathematical model. There wasn't really a conundrum. When the study writes: > Moreover, randomized clinical trials show inconsistent or inconclusive results, with some studies reporting only a marginal benefit or no effect of mask use (5, 6). , the two studies they cite with inconclusive data are ridiculously weak. The first one (their "5") is [https://academic.oup.com/jid/article/201/4/491/861190 https://academic.oup.com/jid/article/201/4/491/861190]. This was published in 2010, with data from 2006-to-2007, for "influenza-like illness" (not SARS-CoV-2, nor even influenza (explained below)). Apparently they asked students living in the dorms to do certain behaviors for weeks at a time. They concluded: > Conclusions: These findings suggest that face masks and hand hygiene may reduce respiratory illnesses in shared living settings and mitigate the impact of the influenza A(H1N1) pandemic. And if that sounds inconclusive, yeah.. their study was ridiculously under-powered. In fact: > This study has several limitations. First, influenza incidence was low, so it is likely that most ILI cases were not associated with influenza infection, even though the study was conducted during the influenza season. So not only were they not writing about COVID, apparently the authors argue that most of the cases probably weren't even influenza. There're other huge problems with this study too. The second one (their "6") is [https://pubmed.ncbi.nlm.nih.gov/33205991/ https://pubmed.ncbi.nlm.nih.gov/33205991/]. This study assigned subjects a recommendation to wear masks -- presumably some who were recommended to wear masks didn't, while some who weren't recommended to wear masks did. Even then, their statistical analysis was very noisy: > Although the difference observed was not statistically significant, the 95% CIs are compatible with a 46% reduction to a 23% increase in infection. And their stated limitations: > Limitation: Inconclusive results, missing data, variable adherence, patient-reported findings on home tests, no blinding, and no assessment of whether masks could decrease disease transmission from mask wearers to others. Point being that there's not really a conundrum related to things not fitting together so much as a simple lack of good data.
- 5y ago
panarky 5y ago
> The effectiveness of masks, however, is still under debate Effective for the mask wearer, or effective for others in the vicinity of the mask wearer? It's well established that cheap cloth masks and procedure masks don't protect the mask wearer very much. The rationale for cheap masks is that they drastically reduce the spread of particles from the wearer to everyone else nearby. If your goal is to protect yourself, wear an N95 or better. If your goal is to protect a population, and N95s aren't available, then the cheap mask help a lot when people wear them.
- __blockcipher__ 5y ago
  Except there is no convincing evidence that they actually do help others, and the whole theoretical mechanism is centered around catching large respiratory droplets which is at odd with the totality of evidence pointing towards aerosol being the dominant mode. I would add if droplet transmission is the dominant mode, which I very much doubt, then masks would still fail in a real-world setting when you look at the fact they make conversational partners stand closer or speak louder, and the massive cross contamination that happens to almost everybody wearing these pieces of cloth over their faces (hands touch mask, mask touches hands, etc)
  - panarky 5y ago
    > no convincing evidence This MIT study [0] was pretty convincing. They conclude that "face masks can be an extremely effective indoor safety measure". For example: If an infected person was riding on a commercial airline with 100 other people, other passengers would be at risk of infection within 70 minutes. If all of the passengers wore masks, however, that space could be safe for up to 54 hours. [0] https://www.pnas.org/content/118/17/e2018995118 https://www.pnas.org/content/118/17/e2018995118
    - nradov 5y ago
      How can a model be convincing if it hasn't been extensively tested in the real world?
jonplackett 5y ago
I really don’t get why this is still considered a conundrum Lots of places have R hovering around 1. If it goes to 1.1 everything goes to shit, if it drops to 0.9. Everything will be fine. So even if masks reduce spread by a tiny amount, even 10% better. That could easily swing you below 1 and save the day.
- deleted 5y ago
  [deleted]
- nostrebored 5y ago
  10% would not be tiny, that would be a statistically huge percentage based on population counts.
- beagle3 5y ago
  The CDC study concluded 2% reduction. That’s in the range where harms need to be weighed too (e.g. masks that aren’t replaced often enough harbor bacteria themselves; there’s environmental costs, etc)
- makomk 5y ago
  The trouble is that this doesn't actually work. By using R this way you're assuming a model where every person is equally likely to spread the infection to every other person in the population, which is easy to calculate but what actually happens. In reality people can only spread the virus to those they're in contact with, and (say) a supermarket employee can spread the virus to more people than someone working from home and not socializing due to social distancing rules. Not only that, there are clusters of people who are all likely to spread the virus to more people or to less people when infected, such as workers in food manufacturing, people in dense urban areas vs less dense areas, etc... So what actually happens in reality is that if R is hovering around 1, there are going to be some places where it's actually above 1 and cases are growing exponentially, and some where it's below 1 and they're shrinking exponentially. The end result of this is that places where R is actually below 1 make up an exponentially shrinking proportion of all cases, and as this happens it causes the overall measurement of R to go back above 1.
andreygrehov 5y ago
> observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease Which is also not entirely true. There are quite a lot of regions (data from worldometer, statista) that have a better control of the virus despite people not giving a crap about face masks. For instance, Florida has 1600 deaths/M vs 3000 deaths/M in New Jersey. What'd be the explanation?
- deleted 5y ago
  [deleted]
- fancifalmanima 5y ago
  https://www.worldometers.info/coronavirus/usa/new-jersey/ https://www.worldometers.info/coronavirus/usa/new-jersey/ https://www.worldometers.info/coronavirus/usa/florida/ https://www.worldometers.info/coronavirus/usa/florida/ It looks like New Jersey was hit early on (when it was also rampant in New York) and Florida got hit later. It could be that hospitals do better at treating it now. Obviously that's speculative. But there are like 30 things I could think of that would make it difficult to make direct comparisons between states. Climate is another one -- Florida is nice all year round, so you can have family/friend gatherings outdoors. I also live in a warm state, and we've just done family/friend stuff outside, even Christmas. At this point we do things indoors when everyone there is vaccinated, and outdoors otherwise. In the case of Florida, turns out all those people that ignored restrictions and went to the beach were something like like 20x less likely to spread it than people spending time indoors. Again... speculative. Point being, you'd have to somehow have the data you need to properly control for a multitude of factors if you wanted to make direct comparisons (including some solid reasoning on what to control for).
- boplicity 5y ago
  I don't understand this myth about Florida. It has fared very badly in the pandemic. You're three times as likely to have died in Florida from COVID, as opposed to in Canada. It sits in the middle of the States, in terms of death rates, which overall have been among the worst in the world. Compare your example to an area where people really take masking serious, such as Hong Kong, and then maybe you'll have a valid comparison.
addicted 5y ago
Considering that the vast majority of cases of COVID are asymptomatic, it’s pretty apparent that the viral load needed to infect someone enough that they even exhibit symptoms, never mind need to be hospitalized, is not easy to achieve. As such, it’s likely even a 30% reduction (which is on the lower end of the range) in the viral load inhaled by someone could drastically reduce the chance of symptomatic COVID. And when you combine 30% reductions for both the receiver and the emitter, it gets much higher.
- maxerickson 5y ago
  That's not how infections work though. A high initial load can cause the infection to peak higher (because more replication occurs before the immune response), but a lower initial load doesn't necessarily lead to a low peak infection (because replication is exponential with a large exponent).
  - chimprich 5y ago
    That doesn't make a lot of sense. Higher initial load means higher severity but a lower initial load doesn't mean lower severity?
    - maxerickson 5y ago
      A lower initial load doesn't guarantee a low severity because the timing of the immune response is such a big factor (due to the large reproduction exponent). As such, it’s likely even a 30% reduction (which is on the lower end of the range) in the viral load inhaled by someone could drastically reduce the chance of symptomatic COVID. is vague enough to not be an over statement, but it probably isn't easy to find much in the way of actual support for it either.
      - chimprich 5y ago
        A lower initial load leading to less severe disease makes intuitive sense (less opportunity for the infection to outpace the immune response) and whilst not proved, a lot of virology experts think it's plausible. There is at least some evidence for it, e.g. a military base study that found less severe disease cases once masks started being worn.
raverbashing 5y ago
Ah yes the "randomized controlled" studies 5 and 6. 5 is about influenza and 6 is not even worth the paper it's printed on. No kidding, 6 is "recommending" people to wear a mask (and not even trying to control for the actual number). So no, I have no qualms in calling study 6 useless, I've seen science fair projects with more scientific rigor and relevance than that.

by rsj_hn 5y ago

BugsJustFindMe 5y ago

The mistake that many people make, and that I think you're implicitly making here too, is this notion of "controlled study". If the study denies the result seen time and again in real life, perhaps the study isn't studying correctly.

colonelanguz 5y ago
How many agains makes the study wrong
bawolff 5y ago
If we fully understood what was happening in real life, we wouldn't need studies.

function_seven 5y ago

> On the other hand, "observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease 2019 (COVID-19) (7–9)." So how to explain these contrasting results and apparent inconsistencies? My hypothesis regarding surgical mask prevalence and how it correlates with better virus control: People who wear masks--however effective they may be--also behave in other ways to limit the spread. They minimize time spent in public indoor spaces, they keep distance from other people, they're more likely to self-quarantine if a family member is sick, etc. The mask-wearing prevalence is a proxy for how serious the wearer takes Covid as a threat.

jasonlaramburu 5y ago
It’s worth also considering the case of ski helmets. Since these have became common on the slopes head trauma has actually increased because wearers take more risks.
- swader999 5y ago
  Probably related to the uptake in snow boarding.
- lostlogin 5y ago
  I had previously read that WW1 saw an increase in head injuries when helmets were used, due to victims surviving previously fatal injuries. However on searching it doesn't seem that clear-cut.
- AuryGlenz 5y ago
  I definitely noticed a change in behavior at stores and at weddings I photographed once the mask mandate happened. Before it happened? Small backyard ceremonies with just families. In stores people straight up avoided being close to others. After? Normal, but with masks.
- function_seven 5y ago
  Yeah, or the idea that maybe helmets in gridiron football increase CTE. I see the possibility, but my own anecdotal experience with mask wearers and non-wearers jives with the other correlation: that non-wearers generally didn’t take the pandemic seriously. The people that I know who shunned masks also ignored the COVID threat in other ways: Large gatherings, vacations to another state to escape lockdown restrictions, etc. Whereas my religiously-masked friends were basically isolated last year. And because I have several such anecdotes, I now have data :)

wrycoder 5y ago

I suspect that in locations with a higher prevalence of masking the population is generally more vigilant: more hand washing, more social distance, stay at home when ill, avoid obviously ill people, and so on. May be a case of correlation, not causation. It would be interesting to have a trial where everyone was wearing N95s, but we're not likely to see that.

carlmr 5y ago
>It would be interesting to have a trial where everyone was wearing N95s, but we're not likely to see that. Bavaria and Austria had FFP2/KN95 only while the rest of Germany had the choice of surgical masks or FFP2, where almost everybody picked surgical masks (cheaper, not as annoying to wear). Now the rest of Germany switched to only FFP2 in public transport. So we do have some population studies. It didn't seem to make much of a difference. I'd say the factor overwhelming almost every other measure is the weather. More people outside means dropping case numbers. More people at home means rising case numbers. It's been true for influenza and cold, and it's still holding up for Corona. If any measure would make sense it would be to allow people to meet outside while forbidding it at home. They only forbade at home without allowing outside meetups, which made home parties more likely.
- tgsovlerkhgsel 5y ago
  Ventilation could also be a factor. You're more likely to open the window when the air outside is pleasant.
  - carlmr 5y ago
    True, which is why it's even more important to get people to meet outside. If you forbid inside and outside meetups, people will meet in secret, even closing their Windows so the neighbors don't snitch (this is Germany after all, the nation of snitches, historically :D). A little bit of basic human psychology could have prevented some of these waves.
asabjorn 5y ago

caddemon 5y ago

The RCTs I have seen with basic surgical masks also seem to focus only on protection of the wearer, whereas on a societal level wearing even a shitty mask may be helping to prevent spread by presymptomatic people. I think it is unlikely the positive outcomes in mask wearing communities are purely due to confounders, although of course they probably also play a role.

splithalf 5y ago
I suspect mask wearing increases social distancing. That would explain much of the data but satisfy neither political party.
- caddemon 5y ago
  I'm not sure about that honestly. At the extreme there's definitely COVID deniers who followed no precautions, but IME most "normal" people I know felt more comfortable spending time indoors with masks than they would have otherwise. And 6 feet is really not enough spacing in many indoor environments. With things like elevators the other person could be gone and you could still be exposing yourself. There is also precedence for some of these statistics with Asian countries during the SARS pandemic, and in these places rule following is generally much better. And with a smaller sample size there are some case studies from restaurant transmission. Staff seem to get infected less frequently than other diners, even though they are in the space for longer. There are a few possible explanations, but the fact that staff don't take their masks off is a pretty compelling one.
  - __blockcipher__ 5y ago
    > Staff seem to get infected less frequently than other diners, even though they are in the space for longer. There are a few possible explanations, but the fact that staff don't take their masks off is a pretty compelling one. IMO that’s the least compelling reason. One big one would be the staff having way more contacts and thus higher exposure to the other circulating hCoVs as well as SARS-2 itself. The evidence for face masks is weak at best. In my opinion they don’t even make sense theoretically unless you pretend that droplet transmission is the dominant transmission mode, which is completely unproven yet widely believed dogma (go figure)

tgsovlerkhgsel 5y ago

What I don't understand... the UK was already doing challenge studies (intentionally infecting consenting volunteers). Why didn't they make one with masks? Really can't be that hard to take a known infected person, sit them on a chair, arrange 100 people around them for a few hours with masks applied in a checkerboard pattern, and observe the results. This is usually out of question for ethical reasons, but they already decided that that wasn't an obstacle, so why not (also) do a study on this? (Or rather, arrange 10x 10 people, in 5 rounds putting a mask on the infected person.)

mattzito 5y ago
The challenge studies they’re doing involve infecting people with measure doses of the virus. An infected person may or may not be shedding at that particular moment. Once they’ve established the MED to infect someone, they could potentially do a study with aerosols and masks, but even then, trying to simulate the right airflow and volume of viral particles is probably too difficult to be practical.

_Nat_ 5y ago

tl;dr- There wasn't really a conundrum to explain related to mask-effectiveness at different levels. Rather, it's more like a lack of good data, as prior studies being cited were ridiculously weak. --- This seems like a largely helpful characterization. However: > So they are left with a conundrum that places which use surgical masks seem to be better off, whereas randomized control studies of surgical masks show little to no benefit. This is what they try to explain with a mathematical model. There wasn't really a conundrum. When the study writes: > Moreover, randomized clinical trials show inconsistent or inconclusive results, with some studies reporting only a marginal benefit or no effect of mask use (5, 6). , the two studies they cite with inconclusive data are ridiculously weak. The first one (their "5") is [https://academic.oup.com/jid/article/201/4/491/861190 https://academic.oup.com/jid/article/201/4/491/861190]. This was published in 2010, with data from 2006-to-2007, for "influenza-like illness" (not SARS-CoV-2, nor even influenza (explained below)). Apparently they asked students living in the dorms to do certain behaviors for weeks at a time. They concluded: > Conclusions: These findings suggest that face masks and hand hygiene may reduce respiratory illnesses in shared living settings and mitigate the impact of the influenza A(H1N1) pandemic. And if that sounds inconclusive, yeah.. their study was ridiculously under-powered. In fact: > This study has several limitations. First, influenza incidence was low, so it is likely that most ILI cases were not associated with influenza infection, even though the study was conducted during the influenza season. So not only were they not writing about COVID, apparently the authors argue that most of the cases probably weren't even influenza. There're other huge problems with this study too. The second one (their "6") is [https://pubmed.ncbi.nlm.nih.gov/33205991/ https://pubmed.ncbi.nlm.nih.gov/33205991/]. This study assigned subjects a recommendation to wear masks -- presumably some who were recommended to wear masks didn't, while some who weren't recommended to wear masks did. Even then, their statistical analysis was very noisy: > Although the difference observed was not statistically significant, the 95% CIs are compatible with a 46% reduction to a 23% increase in infection. And their stated limitations: > Limitation: Inconclusive results, missing data, variable adherence, patient-reported findings on home tests, no blinding, and no assessment of whether masks could decrease disease transmission from mask wearers to others. Point being that there's not really a conundrum related to things not fitting together so much as a simple lack of good data.

5y ago

panarky 5y ago

> The effectiveness of masks, however, is still under debate Effective for the mask wearer, or effective for others in the vicinity of the mask wearer? It's well established that cheap cloth masks and procedure masks don't protect the mask wearer very much. The rationale for cheap masks is that they drastically reduce the spread of particles from the wearer to everyone else nearby. If your goal is to protect yourself, wear an N95 or better. If your goal is to protect a population, and N95s aren't available, then the cheap mask help a lot when people wear them.

__blockcipher__ 5y ago
Except there is no convincing evidence that they actually do help others, and the whole theoretical mechanism is centered around catching large respiratory droplets which is at odd with the totality of evidence pointing towards aerosol being the dominant mode. I would add if droplet transmission is the dominant mode, which I very much doubt, then masks would still fail in a real-world setting when you look at the fact they make conversational partners stand closer or speak louder, and the massive cross contamination that happens to almost everybody wearing these pieces of cloth over their faces (hands touch mask, mask touches hands, etc)
- panarky 5y ago
  > no convincing evidence This MIT study [0] was pretty convincing. They conclude that "face masks can be an extremely effective indoor safety measure". For example: If an infected person was riding on a commercial airline with 100 other people, other passengers would be at risk of infection within 70 minutes. If all of the passengers wore masks, however, that space could be safe for up to 54 hours. [0] https://www.pnas.org/content/118/17/e2018995118 https://www.pnas.org/content/118/17/e2018995118
  - nradov 5y ago
    How can a model be convincing if it hasn't been extensively tested in the real world?

jonplackett 5y ago

I really don’t get why this is still considered a conundrum Lots of places have R hovering around 1. If it goes to 1.1 everything goes to shit, if it drops to 0.9. Everything will be fine. So even if masks reduce spread by a tiny amount, even 10% better. That could easily swing you below 1 and save the day.

deleted 5y ago
[deleted]
nostrebored 5y ago
10% would not be tiny, that would be a statistically huge percentage based on population counts.
beagle3 5y ago
The CDC study concluded 2% reduction. That’s in the range where harms need to be weighed too (e.g. masks that aren’t replaced often enough harbor bacteria themselves; there’s environmental costs, etc)
makomk 5y ago
The trouble is that this doesn't actually work. By using R this way you're assuming a model where every person is equally likely to spread the infection to every other person in the population, which is easy to calculate but what actually happens. In reality people can only spread the virus to those they're in contact with, and (say) a supermarket employee can spread the virus to more people than someone working from home and not socializing due to social distancing rules. Not only that, there are clusters of people who are all likely to spread the virus to more people or to less people when infected, such as workers in food manufacturing, people in dense urban areas vs less dense areas, etc... So what actually happens in reality is that if R is hovering around 1, there are going to be some places where it's actually above 1 and cases are growing exponentially, and some where it's below 1 and they're shrinking exponentially. The end result of this is that places where R is actually below 1 make up an exponentially shrinking proportion of all cases, and as this happens it causes the overall measurement of R to go back above 1.

andreygrehov 5y ago

> observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease Which is also not entirely true. There are quite a lot of regions (data from worldometer, statista) that have a better control of the virus despite people not giving a crap about face masks. For instance, Florida has 1600 deaths/M vs 3000 deaths/M in New Jersey. What'd be the explanation?

deleted 5y ago
[deleted]
fancifalmanima 5y ago
https://www.worldometers.info/coronavirus/usa/new-jersey/ https://www.worldometers.info/coronavirus/usa/new-jersey/ https://www.worldometers.info/coronavirus/usa/florida/ https://www.worldometers.info/coronavirus/usa/florida/ It looks like New Jersey was hit early on (when it was also rampant in New York) and Florida got hit later. It could be that hospitals do better at treating it now. Obviously that's speculative. But there are like 30 things I could think of that would make it difficult to make direct comparisons between states. Climate is another one -- Florida is nice all year round, so you can have family/friend gatherings outdoors. I also live in a warm state, and we've just done family/friend stuff outside, even Christmas. At this point we do things indoors when everyone there is vaccinated, and outdoors otherwise. In the case of Florida, turns out all those people that ignored restrictions and went to the beach were something like like 20x less likely to spread it than people spending time indoors. Again... speculative. Point being, you'd have to somehow have the data you need to properly control for a multitude of factors if you wanted to make direct comparisons (including some solid reasoning on what to control for).
boplicity 5y ago
I don't understand this myth about Florida. It has fared very badly in the pandemic. You're three times as likely to have died in Florida from COVID, as opposed to in Canada. It sits in the middle of the States, in terms of death rates, which overall have been among the worst in the world. Compare your example to an area where people really take masking serious, such as Hong Kong, and then maybe you'll have a valid comparison.

addicted 5y ago

Considering that the vast majority of cases of COVID are asymptomatic, it’s pretty apparent that the viral load needed to infect someone enough that they even exhibit symptoms, never mind need to be hospitalized, is not easy to achieve. As such, it’s likely even a 30% reduction (which is on the lower end of the range) in the viral load inhaled by someone could drastically reduce the chance of symptomatic COVID. And when you combine 30% reductions for both the receiver and the emitter, it gets much higher.

maxerickson 5y ago
That's not how infections work though. A high initial load can cause the infection to peak higher (because more replication occurs before the immune response), but a lower initial load doesn't necessarily lead to a low peak infection (because replication is exponential with a large exponent).
- chimprich 5y ago
  That doesn't make a lot of sense. Higher initial load means higher severity but a lower initial load doesn't mean lower severity?
  - maxerickson 5y ago
    A lower initial load doesn't guarantee a low severity because the timing of the immune response is such a big factor (due to the large reproduction exponent). As such, it’s likely even a 30% reduction (which is on the lower end of the range) in the viral load inhaled by someone could drastically reduce the chance of symptomatic COVID. is vague enough to not be an over statement, but it probably isn't easy to find much in the way of actual support for it either.
    - chimprich 5y ago
      A lower initial load leading to less severe disease makes intuitive sense (less opportunity for the infection to outpace the immune response) and whilst not proved, a lot of virology experts think it's plausible. There is at least some evidence for it, e.g. a military base study that found less severe disease cases once masks started being worn.

raverbashing 5y ago

Ah yes the "randomized controlled" studies 5 and 6. 5 is about influenza and 6 is not even worth the paper it's printed on. No kidding, 6 is "recommending" people to wear a mask (and not even trying to control for the actual number). So no, I have no qualms in calling study 6 useless, I've seen science fair projects with more scientific rigor and relevance than that.