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There are studies that show that masks (surgical and n95) can help prevent healthy people from getting infected [1][2]. Everyone I've seen claiming the opposit

There are studies that show that masks (surgical and n95) can help prevent healthy people from getting infected [1][2]. Everyone I've seen claiming the opposite (including supposed experts being interviewed) usually do it without any significant data to back it up (just some high level theorizing). I also rarely see anyone discussing the nuances of efficacy against airborne vs droplet spread viruses. Using just a minimum amount of reasoning it would seem very plausible that masks would be effective against droplets but less effective against airborne diseases. [1] https://www.newscientist.com/article/dn3692-face-masks-are-best-protection-against-sars/ https://www.newscientist.com/article/dn3692-face-masks-are-b... [2] https://annals.org/aim/fullarticle/744899/facemasks-hand-hygiene-prevent-influenza-transmission-households-cluster-randomized-trial https://annals.org/aim/fullarticle/744899/facemasks-hand-hyg...

_-___________-_ 7y ago
Public health authorities like CDC don't recommend their use among people who are not infected: CDC does not recommend that people who are well wear [a] facemask to protect themselves from respiratory viruses, including 2019-nCoV. - https://www.cdc.gov/coronavirus/2019-ncov/about/prevention-treatment.html https://www.cdc.gov/coronavirus/2019-ncov/about/prevention-t... Now, I'm not one to blindly trust a government agency, but most of the evidence seems inconclusive at this point, and one thing can't be ignored: in mainland China, use of masks in public spaces is near 100%, yet the virus is spreading rapidly. Outside mainland China, far fewer people are wearing masks, yet the virus is not spreading much at all.
- zxcmx 7y ago
  Not quite sure I get the reasoning in that link. Sure, it's not likely to decrease your direct infection risk. But it does decrease the risk of you infecting others. At any given time you can't really know if you're infected or not if the virus is widespread. Also the mask would presumably be more effective than coughing into your elbow or a tissue, which they do recommend. So why not wear them? Why recommend them for healthcare workers but not the general public? I'm wondering if the unstated reasoning is that widespread mask usage freaks people out and increases the chance of large scale panic.
  - _-___________-_ 7y ago
    > At any given time you can't really know if you're infected or not if the virus is widespread. Unless you're in China, the virus is not widespread. I imagine they would change their recommendation if it was. > So why not wear them? Why recommend them for healthcare workers but not the general public? The chance that a healthcare worker who is treating a suspected CoV case is in close contact with an infected patient is close to 100%. On the other hand, the chance that a member of the general public outside of mainland China comes into close contact with someone who is infected, whether they're in the rest of Asia or not, is within a few orders of magnitude of 0.00001%.
    - zxcmx 7y ago
      Yes, totally agree. I wonder what the rational tipping point would be for mask vs no mask.
    - ericb 7y ago
      1-Since travel is still occuring out of mainland China, your faith in the virus being limited to the nation of China seems misplaced. 2-Your estimates of the probability are unlikely shift properly as the landscape of infection changes rapidly, and is not apparent to the naked eye. Humans intuitively do not tend to comprehend exponential/quadratic growth. This video outlines it. The main point is to look how late, in this scenario you'd be saying "no problem" and how quickly it goes from fine, to effed. Note: this is not an endorsement on the other items in this channel, I just think this particular explanation is demonstrative. https://www.youtube.com/watch?v=iIwyMif5EOg&feature=youtu.be&fbclid=IwAR1P0VtpPW7MLN5dLpjt83cRb0lQBDn5kb-HccyjTGYE1rC0CRgsCRCAUt8 https://www.youtube.com/watch?v=iIwyMif5EOg&feature=youtu.be...
      - _-___________-_ 7y ago
        > 1-Since travel is still occuring out of mainland China, your faith in the virus being limited to the nation of China seems misplaced. I never said it was limited to the nation of China, I said it wasn't widespread outside of China and a cruise ship, which remains true despite significant travel still occurring. Humans are also terrible at intuitively assessing risk, and the current panic is a great example of this.
- ethbro 7y ago
  > Public health authorities like CDC don't recommend their use among people who are not infected See: https://www.cdc.gov/coronavirus/2019-ncov/hcp/index.html https://www.cdc.gov/coronavirus/2019-ncov/hcp/index.html Your link & the CDC don't say what you think they say. CDC's recommendations are that members of the uninfected public should not wear N95 masks. This should NOT be understood as: CDC says N95 masks are ineffective at preventing airborne infections of Covid-19. It IS the CDC saying: N95 masks are non-trivial to use correctly, require decontamination protocols or single-use replacement to avoid infection and contamination from used masks themselves (potentially full of virus particles), and protect against a threat many people are unlikely to be exposed to (close proximity infected persons) -- a mix of criteria that make them inefficient to recommend for general public use. As you see in the link above, CDC absolutely recommends N95+ respirators for EMS and healthcare workers, when working in close proximity to infected persons. But healthcare workers have a substantially higher airborne exposure risk, as well as professional support and training for properly using N95 masks.
  - _-___________-_ 7y ago
    They do say what I think they say, but yeah, I should have clarified that I meant the public, not healthcare workers. (I addressed this more clearly in another comment on the same submission.)

_-___________-_ 7y ago

Public health authorities like CDC don't recommend their use among people who are not infected: CDC does not recommend that people who are well wear [a] facemask to protect themselves from respiratory viruses, including 2019-nCoV. - https://www.cdc.gov/coronavirus/2019-ncov/about/prevention-treatment.html https://www.cdc.gov/coronavirus/2019-ncov/about/prevention-t... Now, I'm not one to blindly trust a government agency, but most of the evidence seems inconclusive at this point, and one thing can't be ignored: in mainland China, use of masks in public spaces is near 100%, yet the virus is spreading rapidly. Outside mainland China, far fewer people are wearing masks, yet the virus is not spreading much at all.

zxcmx 7y ago
Not quite sure I get the reasoning in that link. Sure, it's not likely to decrease your direct infection risk. But it does decrease the risk of you infecting others. At any given time you can't really know if you're infected or not if the virus is widespread. Also the mask would presumably be more effective than coughing into your elbow or a tissue, which they do recommend. So why not wear them? Why recommend them for healthcare workers but not the general public? I'm wondering if the unstated reasoning is that widespread mask usage freaks people out and increases the chance of large scale panic.
- _-___________-_ 7y ago
  > At any given time you can't really know if you're infected or not if the virus is widespread. Unless you're in China, the virus is not widespread. I imagine they would change their recommendation if it was. > So why not wear them? Why recommend them for healthcare workers but not the general public? The chance that a healthcare worker who is treating a suspected CoV case is in close contact with an infected patient is close to 100%. On the other hand, the chance that a member of the general public outside of mainland China comes into close contact with someone who is infected, whether they're in the rest of Asia or not, is within a few orders of magnitude of 0.00001%.
  - zxcmx 7y ago
    Yes, totally agree. I wonder what the rational tipping point would be for mask vs no mask.
  - ericb 7y ago
    1-Since travel is still occuring out of mainland China, your faith in the virus being limited to the nation of China seems misplaced. 2-Your estimates of the probability are unlikely shift properly as the landscape of infection changes rapidly, and is not apparent to the naked eye. Humans intuitively do not tend to comprehend exponential/quadratic growth. This video outlines it. The main point is to look how late, in this scenario you'd be saying "no problem" and how quickly it goes from fine, to effed. Note: this is not an endorsement on the other items in this channel, I just think this particular explanation is demonstrative. https://www.youtube.com/watch?v=iIwyMif5EOg&feature=youtu.be&fbclid=IwAR1P0VtpPW7MLN5dLpjt83cRb0lQBDn5kb-HccyjTGYE1rC0CRgsCRCAUt8 https://www.youtube.com/watch?v=iIwyMif5EOg&feature=youtu.be...
    - _-___________-_ 7y ago
      > 1-Since travel is still occuring out of mainland China, your faith in the virus being limited to the nation of China seems misplaced. I never said it was limited to the nation of China, I said it wasn't widespread outside of China and a cruise ship, which remains true despite significant travel still occurring. Humans are also terrible at intuitively assessing risk, and the current panic is a great example of this.
ethbro 7y ago
> Public health authorities like CDC don't recommend their use among people who are not infected See: https://www.cdc.gov/coronavirus/2019-ncov/hcp/index.html https://www.cdc.gov/coronavirus/2019-ncov/hcp/index.html Your link & the CDC don't say what you think they say. CDC's recommendations are that members of the uninfected public should not wear N95 masks. This should NOT be understood as: CDC says N95 masks are ineffective at preventing airborne infections of Covid-19. It IS the CDC saying: N95 masks are non-trivial to use correctly, require decontamination protocols or single-use replacement to avoid infection and contamination from used masks themselves (potentially full of virus particles), and protect against a threat many people are unlikely to be exposed to (close proximity infected persons) -- a mix of criteria that make them inefficient to recommend for general public use. As you see in the link above, CDC absolutely recommends N95+ respirators for EMS and healthcare workers, when working in close proximity to infected persons. But healthcare workers have a substantially higher airborne exposure risk, as well as professional support and training for properly using N95 masks.
- _-___________-_ 7y ago
  They do say what I think they say, but yeah, I should have clarified that I meant the public, not healthcare workers. (I addressed this more clearly in another comment on the same submission.)