I wanted to know about this for a while. I wonder like when I buy something and look in the bag or container and one is totally bad but the rest look normal, or most of them look normal, are they all still bad? I bought these kumkuats and when I opened the bag the next day one was full of fuzzy mold all over it, so I threw it out. The rest looked normal though and I couldn't see anything on them. Yet obviously they were touching the other one. Does that spread and ruin them before you can even see it? Does washing them clean them off enough from what they were touching or are they unsafe. I was also wondering when you find something in your fridge, like in the back of your fridge that you kept overlooking and didn't know was there and it is really spoiled and bad, does that go and ruin everything in the fridge that was uncovered? Just go and contaminate everything in the same enclosed space? I need to know.

Same thing with Cherry tomatoes a lot, buy a box of them and some might be bad. Is it safe only to discard the visibly bad ones?

No. If you have a moldy fruit, and there are other overripe fruit in the batch, they will get mold also, whether or not they touch the moldy one. However, the ones that are not overripe are impervious to the mold unless they become overripe or get damaged.

Thanks. I heard the spores get airborne and attach to everything. So I guess I will just wash them really well in a vinegar bath then.