Coronavirus Disease 2019 (COVID-19)

[Undertoad]

And a commenter tells us why cloth masks like bandanas don't really work, and it's immediately understandable:

The droplet that would have entered your mouth instead lands on the fabric, where the water evaporates, leaving airborne virus that you inhale.

N95 masks work in part because the holes in the mask/filter media are smaller than some dimensions of the virus. Fabric has holes on the micron scale.