[achenatx]

the risk reduction is actually very high. But the probability of being in the presence of the virus is very low. Health care workers treating infected patients have a 100% chance of being exposed so epidemiological risk reduction is large.

I think the "useless" part actually refers to the the fact that the public at large wont be wearing masks so a few people wearing masks might protect themselves, but does nothing to alleviate the overall spread of the virus.

[PeterisP]

The probability for being in the presence of the virus is very low right now in USA, but it's quite high in many other places (e.g. Iran) right now and in USA in the near future.

If media can be pushed to destigmatize wearing of masks and stigmatize not wearing of masks, then this (combined with starting manufacturing large quantities of masks) would alleviate the overall spread of the virus in the post-containment mitigation phase, in which many countries are right now.

[JoeAltmaier]

I understand that wearing a mask doesn't prevent the wearer (for most common masks) but instead protects other people. Should you be a carrier. It slows the spread, which is a good thing?

[kps]

It's a matter of terminology; ‘mask’ has a narrower meaning than in colloquial use. https://www.cdc.gov/niosh/npptl/pdfs/UnderstandDifferenceInf...

(Compounding the confusion is that a reusable rubber respirator is also called a ‘half mask’.)

[mhb]

What is your basis for this? My understanding is that an N95 mask, worn by following the directions on the box, provides significant protection to the wearer. Also, if it has a vent for exhaling, that would suggest it is not necessarily such good protection for others.