[wegs]

For public health use (as opposed to medical use), the difference between an N95 mask and a surgical mask is pretty small. They both make a huge difference.

It's true: air can come around if the seal isn't perfect. However, you've eliminated most of the virus. At that point, other modes of spread become dominant.

In a medical setting, where you're guarding against all modes of spread with a full body suit, googles, etc., and where you're dealing with large numbers of exposures, it's a completely different story.

Ballpark numbers for masks+frequent handwashing suggest that they'd bring R0 close to 1, assuming a whole bunch of unvalidated assumptions (e.g. they have the same impact on coronavirus as on the flu). At that point, we should be able to get things under control with social distancing and similar measures.