What I've read about Coronaviruses is that most transmission is either through hand to face contact or droplet-suspended virions so a mask that doesn't protect against aerosolized droplets would still be fairly effective. I understand that surgical masks aren't intended to prevent inhalation of droplets but the substantial symmetry between air passing through one way or the other would suggest at least broadly similar effects either way. Given the empirical results from elsewhere in the thread it seems like that may be the case.

Are surgical masks sealed around the edges? I've only worn N95 before and if you don't have a proper seal you're not even filtering the air. That's what I've always assumed was the problem with surgical masks. It's not that they're not a good enough filter, it's that they aren't even filtering the air when you breath in. But I might be wrong.

> N95 masks are meant to protect the wearer from particulate matter (harmful dust) in the air, specifically those particles over 30 microns. SARS-CoV02 is roughly half the size, so as an aerosolized virion, as opposed to droplet-suspended virions, they may have limited effect.

The N95 filters are tested with particles at 30 microns, but that doesn't say anything about their effectiveness against other particles.

3M, naturally, has released some information on this exact topic [1] which goes into a fair bit of detail on the various methods by which masks effect filtration. The tl;dr version is that there are several ways by which filtration is achieved that generally overlap and work towards providing effective protection well above and below 30um. There is generally a small dip in the transition between two primary methods which creates a specific size range where filtration is less effective.

Whether that's an issue depends on your definition of "limited effect". For the masks they tested, that dip generally occurred around 0.04-0.1um. Even in the worst case scenario, however, the worst masks tested were still filtering ~94% of the particles (in a mask that only claims 95% effectiveness to begin with). The linked document has coronaviruses listed as being about 0.125um in size, which has them falling toward the end of the dip where the mask is trending back towards 100% efficacy.

(For what it's worth, they also have the distribution of droplet sizes in a sneeze and they are all smaller than 30um as well. However they're still in a range where the mask will be about 100% effective.)

Which is all to say I certainly wouldn't describe an N95 mask as being of "limited effect".

[1] https://multimedia.3m.com/mws/media/409903O/respiratory-prot...

And as to that not our culture comment, I mean it's the American of course who got told to isolate himself on suspicion of infection but decided to go to a group political event across state lines regardless, only to infect at least one other person and lead to further isolation calls for everyone else he came into contact with.