There are a bunch of variables here that we need to know to be able to say whether any type of mask reduces the likelihood of infecting others, and the percentage of viral particles filtered by the mask is just one of them.
Another key factor is the rate at which the risk of infection changes depending on the percentage of particles filtered.
For instance, it's conceivable that you can be equally likely to be infected whether 5% or 95% of particles are filtered, depending on the "potency" of the particles that are not filtered. If contact with just N particles increases a person's likelihood of infection by some percentage, and the average cough transmits 100N particles, then even if you filter out 95% of those, you're still at 5N.
But we know that in most cases, increasing the percentage of filtered particles maps in some way (though maybe not linearly) with reducing the number of infections.
All that is to say: I think we need to be careful about using this one variable -- percentage of particles filtered -- when talking about effectiveness of masks. Effectiveness is more of a holistic calculation, taking into account viral potency, the distance unfiltered viral particles travel through the mask, the degree to which they linger in the air, etc.
MacIntyre (2015):
Use of cloth masks instead of surgical masks increased the risk of infection by 13x (95% CI: 1.69x to 100x). Cloth masks filtered out only 3% of particles, versus 56% for surgical masks.
https://bmjopen.bmj.com/content/5/4/e006577.short
Overall, these findings are suggestive that the infection protection factors are broadly similar to the total filtration efficiencies.
yes, please keep adding level-headed reasoning to the conversation despite the continuing public panic over the topic.
another major confounding variable that makes those effectiveness claims misleading is the environment in which they're used. ENT surgeons (and their patients) are absolutely positively at heightened risk by literally being in the face of patients for prolonged periods. they should use all sorts of countermeasures, including surgical masks.
the typical person on the street gains no added benefit from wearing a mask, regardless of the effectiveness of a given mask at blocking particles, as the ambient viral concentration is effectively non-existent basically everywhere outside, assuming most folks aren't congregating (closely and face-to-face) regularly. even in most indoor situations, mask effectiveness only comes into play in very specific situations.
if no one shoots the ball, you can't block their shot, no matter how great a shot-blocker you are.
latching onto miraculous prophylactics without skepticism and thought is a danger in itself.
> even in most indoor situations, mask effectiveness only comes into play in very specific situations.
I think you might be underestimating how transmissible this particular virus is. If it were that hard to catch it, people wouldn't be catching it at the rate they are.
no, note that the confirmed infection rate as of this morning in CA is 0.1% (~40K out of ~40M). because of the roughly 2-3 week lag in effects, the moderation of that rate is mostly attributable to modest distancing rules, before masks were widely encouraged.
Another key factor is the rate at which the risk of infection changes depending on the percentage of particles filtered.
For instance, it's conceivable that you can be equally likely to be infected whether 5% or 95% of particles are filtered, depending on the "potency" of the particles that are not filtered. If contact with just N particles increases a person's likelihood of infection by some percentage, and the average cough transmits 100N particles, then even if you filter out 95% of those, you're still at 5N.
But we know that in most cases, increasing the percentage of filtered particles maps in some way (though maybe not linearly) with reducing the number of infections.
All that is to say: I think we need to be careful about using this one variable -- percentage of particles filtered -- when talking about effectiveness of masks. Effectiveness is more of a holistic calculation, taking into account viral potency, the distance unfiltered viral particles travel through the mask, the degree to which they linger in the air, etc.