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So IF I read this correctly, cloth masks still do a pretty good job? The post ends with... "I have reanalysed the Korean data using the suggested replacement v

So IF I read this correctly, cloth masks still do a pretty good job? The post ends with... "I have reanalysed the Korean data using the suggested replacement value of half the LOD and the results don’t change very much, suggesting a reduction of 70% of virus particles when using cloth masks." And it starts with... "His key claim is that “cotton masks reduce virus emitted duringcoughing by 96%”, citing a recent South Korean study." So 70% isn't as good as 96%, but it seems like that's still a decent number. Or am I reading this wrong?

shamino 7y ago
When giving out numbers scientifically, it's important to be precise, or have the uncertainty known. In that case, 96% is widely different than 70%. As Andy Slavitt says in his April 22 podcast, when someone claims to know something too precisely in regards to this pandemic, and they don't say "we don't know" enough, run the other direction.
- shamino 7y ago
  You also want to have someone doing a scientific study to be as unbiased as possible. As I understand it, (most of?) his family is immunocompromised. This doesn't mean he shouldn't do it, nor that what he's doing is not saving millions of lives, but it's a little easier to question the "salesmanship" aspect of it when he hasn't spent a lot of time in the field.
gerry_shaw 7y ago
"Cloth masks reduces virus from coughing by 96%" vs "Cloth masks tested on 4 people reduces virus from coughing by 70%" If that is the only study being citied to go against public health officers I'm be skeptical. If cloth masks work it should be feasible to do a larger study and prove it with a high degree of confidence.
bambax 7y ago
The study that finds 70% effectiveness was based on just 4 people, one of whom couldn't produce virus particles even without a mask. Another most serious study based on over 1500 hospital workers found that cloth masks let through over 95% of particles. That more serious study was done in 2015 but there's no reason to think it would not still be correct.
bcoates 7y ago
No, 70% isn't nearly enough. A single contamination event (like a cough) is in the neighborhood of a million virus particles to stop. Think about hand sanitizers: some advertise 99.9% reduction, which is "millions become thousands", bare-minimum levels of actually reducing risk of infection from an exposure. 70% is like "millions become fewer millions"
- marcosdumay 7y ago
  70% is "a 2m safety distance becomes some X, that isn't very easy to calculate". There's very likely an exponential fall of virus with distance, so it's probably something visibly smaller than 2m, but not by a lot. Besides, that's hardly the only variable at play. The virus doesn't spread on the atmosphere only by dispersion, so the particles energy is relevant. It doesn't spread in only in dry particles, so that ratio is relevant, as is the efficiency in blocking the larger wet particles. And it doesn't spread only by coughing, so the efficiency on normal breathing and speaking is important too. Also, we don't need completely effective barriers for people at the street, this is not ebola. We just need to reduce the virus spread by ~60%. The one thing we know is that the countries where people use masks are having an easier time fighting the virus. We don't really know if it's because of the masks, but it's a good bet.

shamino 7y ago

When giving out numbers scientifically, it's important to be precise, or have the uncertainty known. In that case, 96% is widely different than 70%. As Andy Slavitt says in his April 22 podcast, when someone claims to know something too precisely in regards to this pandemic, and they don't say "we don't know" enough, run the other direction.

shamino 7y ago
You also want to have someone doing a scientific study to be as unbiased as possible. As I understand it, (most of?) his family is immunocompromised. This doesn't mean he shouldn't do it, nor that what he's doing is not saving millions of lives, but it's a little easier to question the "salesmanship" aspect of it when he hasn't spent a lot of time in the field.

gerry_shaw 7y ago

"Cloth masks reduces virus from coughing by 96%" vs "Cloth masks tested on 4 people reduces virus from coughing by 70%" If that is the only study being citied to go against public health officers I'm be skeptical. If cloth masks work it should be feasible to do a larger study and prove it with a high degree of confidence.

bambax 7y ago

The study that finds 70% effectiveness was based on just 4 people, one of whom couldn't produce virus particles even without a mask. Another most serious study based on over 1500 hospital workers found that cloth masks let through over 95% of particles. That more serious study was done in 2015 but there's no reason to think it would not still be correct.

bcoates 7y ago

No, 70% isn't nearly enough. A single contamination event (like a cough) is in the neighborhood of a million virus particles to stop. Think about hand sanitizers: some advertise 99.9% reduction, which is "millions become thousands", bare-minimum levels of actually reducing risk of infection from an exposure. 70% is like "millions become fewer millions"

marcosdumay 7y ago
70% is "a 2m safety distance becomes some X, that isn't very easy to calculate". There's very likely an exponential fall of virus with distance, so it's probably something visibly smaller than 2m, but not by a lot. Besides, that's hardly the only variable at play. The virus doesn't spread on the atmosphere only by dispersion, so the particles energy is relevant. It doesn't spread in only in dry particles, so that ratio is relevant, as is the efficiency in blocking the larger wet particles. And it doesn't spread only by coughing, so the efficiency on normal breathing and speaking is important too. Also, we don't need completely effective barriers for people at the street, this is not ebola. We just need to reduce the virus spread by ~60%. The one thing we know is that the countries where people use masks are having an easier time fighting the virus. We don't really know if it's because of the masks, but it's a good bet.