5 ms·

They don't drive the transmissions the way they do for flu or some forms of common cold but I've seen estimates that 5% or so of infections come from fomites.

They don't drive the transmissions the way they do for flu or some forms of common cold but I've seen estimates that 5% or so of infections come from fomites. It's still worth washing your hands when you come home and take off your mask since it's easy, but it's not going to make much of a dent in the R0. Other sort of masks actually do make a dent in R0. A cloth or surgical mask doesn't provide the level of protection a N95 mask does but they do seem to provide a protection factor of 2 or 3. Nothing you could call safe but enough to reduce the R0 of the disease very significantly if everybody used them.

zaroth 6y ago
Where does this 2-3x factor come from? I just haven’t seen any proof of that. From a macro perspective, masks did not stop the 2nd wave in Italy and France and their mask compliance was the highest in Europe. I don’t think you can claim Italy just didn’t mask hard enough. Flu cases, by comparison, are down something like 99% year over year. So it’s not like I’m saying masks and hand washing don’t work. They appear to work extremely well for flu, they just obviously have failed to stop COVID. If you look at how fearful some people are to even approach someone who isn’t wearing a mask, but then immediately feel safer when the mask goes on, it’s not clear to me a better approach wouldn’t have been “masks do not work, if you don’t want COVID then do not gather inside”.
- Symmetry 6y ago
  Well, you can can put masks on dummies and see what fraction of aerosols of different sizes they stop, you can interview people after an outbreak and find out what protective measure they took and whether they get sick. You can look at which regions introduced mask mandates when and see what statistical result that seems to give on the number of covid cases. There have been an awful lot of studies on this topic over the course of the last 3/4 year and I'm also taking into account a study the WHO did after SARS-1 on mask effectiveness in Beijing. I wouldn't neccesarily have thought beforehand that fraction of particles stopped would line up neatly with reduction in chance of getting the disease but it seems to, at least roughly. EDIT: Oh, and there are animal experiments where they put a layer of mask material between hamster cages and see if it prevents infections in the other cage.
  - irq11 6y ago
    ” You can look at which regions introduced mask mandates when and see what statistical result that seems to give on the number of covid cases. There have been an awful lot of studies on this topic” ...all of which written in the spring, when cases were declining across the northern hemisphere. Subsequently, we’ve seen cases go up around the world, and it doesn’t seem to matter much if they have mask mandates, high self-reported mask compliance, or not. This guy has amassed a huge collection of plots documenting the lack of impact of mask laws on outcomes: https://mobile.twitter.com/ianmSC https://mobile.twitter.com/ianmSC

zaroth 6y ago

Where does this 2-3x factor come from? I just haven’t seen any proof of that. From a macro perspective, masks did not stop the 2nd wave in Italy and France and their mask compliance was the highest in Europe. I don’t think you can claim Italy just didn’t mask hard enough. Flu cases, by comparison, are down something like 99% year over year. So it’s not like I’m saying masks and hand washing don’t work. They appear to work extremely well for flu, they just obviously have failed to stop COVID. If you look at how fearful some people are to even approach someone who isn’t wearing a mask, but then immediately feel safer when the mask goes on, it’s not clear to me a better approach wouldn’t have been “masks do not work, if you don’t want COVID then do not gather inside”.

Symmetry 6y ago
Well, you can can put masks on dummies and see what fraction of aerosols of different sizes they stop, you can interview people after an outbreak and find out what protective measure they took and whether they get sick. You can look at which regions introduced mask mandates when and see what statistical result that seems to give on the number of covid cases. There have been an awful lot of studies on this topic over the course of the last 3/4 year and I'm also taking into account a study the WHO did after SARS-1 on mask effectiveness in Beijing. I wouldn't neccesarily have thought beforehand that fraction of particles stopped would line up neatly with reduction in chance of getting the disease but it seems to, at least roughly. EDIT: Oh, and there are animal experiments where they put a layer of mask material between hamster cages and see if it prevents infections in the other cage.
- irq11 6y ago
  ” You can look at which regions introduced mask mandates when and see what statistical result that seems to give on the number of covid cases. There have been an awful lot of studies on this topic” ...all of which written in the spring, when cases were declining across the northern hemisphere. Subsequently, we’ve seen cases go up around the world, and it doesn’t seem to matter much if they have mask mandates, high self-reported mask compliance, or not. This guy has amassed a huge collection of plots documenting the lack of impact of mask laws on outcomes: https://mobile.twitter.com/ianmSC https://mobile.twitter.com/ianmSC