You gotta be careful around those sponges. One killed my great-aunt Bertha. Snuck up behind her, it did, and . . . .
Well, that’s another story.
Your sponge won’t likely kill you, but it may make you or one of your family members ill. You can’t assume all germs are being killed by the soap you use to wash dishes. Nor does being on a dry surface kill them all, IIRC.
Most likely, you’ll only get an upset tummy from it-- you probably won’t even connect the two, but there are more serious germs which can lurk in a sponge, like salmonella. It’s better safe than sorry. I’d leave off using them all together, if I were you. Dishrags are a much better choice.
However, if you insist, you want to properly maintain your sponge, and towards that end, there are a few things you can do: Soak it overnight in a bleach-water solution frequently-- preferably every time you clean up something germy. Or, put it in the microwave (wet) for a half a minute or so. )Let cool before removing, obviously.)