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You have to read a footnote in the original paper to understand that the “surgical” masks used actually contained a blown fiber layer, like N95s, and passed the

You have to read a footnote in the original paper to understand that the “surgical” masks used actually contained a blown fiber layer, like N95s, and passed the 95% filtration level when tested. These are not the surgical/procedure masks that we see people commonly wearing in the US. Not only that, but they cost thirteen cents apiece. Why don’t we have those in the US? Edit: it’s not a very good trial, because mask compliance was poor in spite of their efforts, and they didn’t separate the mask wearing groups when evaluating the outcomes, though they could have. I would have expected better results from the “surgical” masks. You really have to read the original paper to assess this trial properly.

criticaltinker 5y ago
Great points. It’s worth adding that SARS-COV-2 is spread primarily through the air via extremely tiny droplets (< 5 μm) [1]. Breathing, coughing, and sneezing produces infectious aerosols which can remain suspended in the air for hours. Most cloth masks that are used by the general public will provide very little protection against inhaling or producing these aerosols [2], though such masks are likely to help reduce the spread of larger droplets. [1] Airborne transmission of respiratory viruses https://www.science.org/lookup/doi/10.1126/science.abd9149 https://www.science.org/lookup/doi/10.1126/science.abd9149 [2] Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks https://pubs.acs.org/doi/10.1021/acsnano.0c03252# https://pubs.acs.org/doi/10.1021/acsnano.0c03252#
angelzen 5y ago
> “surgical” masks used actually contained a blown fiber layer, like N95s, and passed the 95% filtration level when tested. > The study’s authors found that surgical masks — but not cloth masks — reduced transmission of SARS-CoV-2 in villages where the research team distributed face masks and promoted their use. West coast city: 90% of the people I see around wear useless cloth masks. Borders on criminal that we pretend the mask-as-virtue-statement circus we are currently undergoing has any benefit other than reduced oxygen flow.
- mike00632 5y ago
  We've gone from quoting a part of the article leaving out the part that discusses cloth mask efficacy to full blown denial of what the study concludes about cloth masks, regurgitation tired old anti-mask rhetoric.
  - angelzen 5y ago
    I'm sorry, please help me: where does the study say cloth masks help?
    - mike00632 5y ago
      "Material difference The study linked surgical masks with an 11% drop in risk, compared with a 5% drop for cloth..."
      - angelzen 5y ago
        Consider taking it up with Lynne Peeples. The very subtitle of the piece is 'surgical masks are highly protective, but cloth masks fall short', I have no idea why she thinks '11% drop in risk' is 'highly protective', but '5% drop' is 'falling short'. Either way the numbers appear marginal at best. Edit: Fundamentally I have an issue with any definition of risk that bounds the measure to a short time frame. For all we know the mask intervention may slow the spread speed by a small factor, but were we to measure over a year (or even longer) we might observe the same total number of infections: the virus is going to infect everyone susceptible, only at a slightly slower pace.
        mike00632 5y ago
        1. Based on the size of the study there are thresholds for statistical significance. 2. Only a portion of the people were even wearing masks. A few people wore masks and the risk of infection dropped by a few percent. Declaring masks don't work because a couple people wore them yet the entire population didn't see a complete decline in infection is illogical and dishonest. 3. The study not being able to conclude in a statistically significant way that cloth masks prevent infection is completely different from concluding that cloth masks are worthless. Your aversion to masks is completely a reflection of your bias and not supported by this study.
abdullahkhalids 5y ago
The other important piece of information in that footnote is that filtration efficiency of cloth masks depend highly on their material and design. I wish it was possible to actually test the filtration efficiency of cloth and surgical masks available in the market.

criticaltinker 5y ago

Great points. It’s worth adding that SARS-COV-2 is spread primarily through the air via extremely tiny droplets (< 5 μm) [1]. Breathing, coughing, and sneezing produces infectious aerosols which can remain suspended in the air for hours. Most cloth masks that are used by the general public will provide very little protection against inhaling or producing these aerosols [2], though such masks are likely to help reduce the spread of larger droplets. [1] Airborne transmission of respiratory viruses https://www.science.org/lookup/doi/10.1126/science.abd9149 https://www.science.org/lookup/doi/10.1126/science.abd9149 [2] Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks https://pubs.acs.org/doi/10.1021/acsnano.0c03252# https://pubs.acs.org/doi/10.1021/acsnano.0c03252#

angelzen 5y ago

> “surgical” masks used actually contained a blown fiber layer, like N95s, and passed the 95% filtration level when tested. > The study’s authors found that surgical masks — but not cloth masks — reduced transmission of SARS-CoV-2 in villages where the research team distributed face masks and promoted their use. West coast city: 90% of the people I see around wear useless cloth masks. Borders on criminal that we pretend the mask-as-virtue-statement circus we are currently undergoing has any benefit other than reduced oxygen flow.

mike00632 5y ago
We've gone from quoting a part of the article leaving out the part that discusses cloth mask efficacy to full blown denial of what the study concludes about cloth masks, regurgitation tired old anti-mask rhetoric.
- angelzen 5y ago
  I'm sorry, please help me: where does the study say cloth masks help?
  - mike00632 5y ago
    "Material difference The study linked surgical masks with an 11% drop in risk, compared with a 5% drop for cloth..."
    - angelzen 5y ago
      Consider taking it up with Lynne Peeples. The very subtitle of the piece is 'surgical masks are highly protective, but cloth masks fall short', I have no idea why she thinks '11% drop in risk' is 'highly protective', but '5% drop' is 'falling short'. Either way the numbers appear marginal at best. Edit: Fundamentally I have an issue with any definition of risk that bounds the measure to a short time frame. For all we know the mask intervention may slow the spread speed by a small factor, but were we to measure over a year (or even longer) we might observe the same total number of infections: the virus is going to infect everyone susceptible, only at a slightly slower pace.
      - mike00632 5y ago
        1. Based on the size of the study there are thresholds for statistical significance. 2. Only a portion of the people were even wearing masks. A few people wore masks and the risk of infection dropped by a few percent. Declaring masks don't work because a couple people wore them yet the entire population didn't see a complete decline in infection is illogical and dishonest. 3. The study not being able to conclude in a statistically significant way that cloth masks prevent infection is completely different from concluding that cloth masks are worthless. Your aversion to masks is completely a reflection of your bias and not supported by this study.

abdullahkhalids 5y ago

The other important piece of information in that footnote is that filtration efficiency of cloth masks depend highly on their material and design. I wish it was possible to actually test the filtration efficiency of cloth and surgical masks available in the market.