I use a dishrag, rather than sponges, for general cleaning. That way I can wash it in hot water and bleach and get lots of uses for each. A sponge is for cleaning the bathroom... and gets tossed.
For my face... I just use my hands. Unfortunately those can't be microwaved.
We live in a world awash in microorganisms, I suspect that most of the things people worry about are pretty unimportant in the larger scheme of things.