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A great explanation of a lot of things, but this looks wrong to me: "To put a number on it: surgical masks on the sick person reduce cold & flu viruses in aeros

by gns24 6y ago

A great explanation of a lot of things, but this looks wrong to me: "To put a number on it: surgical masks on the sick person reduce cold & flu viruses in aerosols by 70%. Reducing transmissions by 70% would be as large an impact as a lockdown!" Reducing the amount of virus in aerosols won't reduce the number of infections by the same amount. If a cough produces ten times the infective dose, then with the mask that's still three times. Masks are still likely to help (and maybe having a smaller dose will make the disease milder if someone does catch the virus), but it's not possible to make a statement like this about the effect on R.

H8crilA 6y ago
Just read the next 4 short paragraphs.
gilbetron 6y ago
From what I've read it's the opposite effect. Wearing masks has a greater effect on reducing propagation (R-value) than expected. https://www.ijidonline.com/article/S1201-9712(08)01008-4/fulltext https://www.ijidonline.com/article/S1201-9712(08)01008-4/ful...
cactus2093 6y ago
I can’t really imagine a mechanism by which a mask would still let the same cloud of particles from a cough disperse in exactly the same way, but uniformly remove 70% of them. Surely if it is blocking that many particles it’s also disrupting the spread of the remaining particles. Or it could very well be the opposite of what you’re saying, maybe blocking that 70% of particles is enough to stop even more than 70% of the transmission opportunities. That wouldn’t be crazy if the spread is mostly via large droplets (most likely to get stopped by a mask) rather than aerosolized particles, which has been suggested. I think your argument is that it’s just not scientifically proven, but we have to make decisions today with the best information we have. Wearing masks still appears to be a good idea, has very low cost, and has been shown to help for a long time for all kinds of respiratory diseases.
- gns24 6y ago
  I don't disagree that wearing masks seems a good idea, I'm just saying 70% reduction in particles doesn't map to a 70% reduction in transmissions. Whether the reduction is 10% or 90%, it's a useful contribution, particularly because in public situations where masks are likely to be recommended (transport, shops) if someone coughs as you're walking past there's no way for contact tracers to know about that link.

by gns24 6y ago

H8crilA 6y ago

Just read the next 4 short paragraphs.

gilbetron 6y ago

From what I've read it's the opposite effect. Wearing masks has a greater effect on reducing propagation (R-value) than expected. https://www.ijidonline.com/article/S1201-9712(08)01008-4/fulltext https://www.ijidonline.com/article/S1201-9712(08)01008-4/ful...

cactus2093 6y ago

I can’t really imagine a mechanism by which a mask would still let the same cloud of particles from a cough disperse in exactly the same way, but uniformly remove 70% of them. Surely if it is blocking that many particles it’s also disrupting the spread of the remaining particles. Or it could very well be the opposite of what you’re saying, maybe blocking that 70% of particles is enough to stop even more than 70% of the transmission opportunities. That wouldn’t be crazy if the spread is mostly via large droplets (most likely to get stopped by a mask) rather than aerosolized particles, which has been suggested. I think your argument is that it’s just not scientifically proven, but we have to make decisions today with the best information we have. Wearing masks still appears to be a good idea, has very low cost, and has been shown to help for a long time for all kinds of respiratory diseases.

gns24 6y ago
I don't disagree that wearing masks seems a good idea, I'm just saying 70% reduction in particles doesn't map to a 70% reduction in transmissions. Whether the reduction is 10% or 90%, it's a useful contribution, particularly because in public situations where masks are likely to be recommended (transport, shops) if someone coughs as you're walking past there's no way for contact tracers to know about that link.