Is that a regional thing? I was under the impression they just popped up every now and then, though I've never heard of any except in stories on Reddit. Don't think I heard anyone mention that it only occurs in a certain climate, and we do have airplanes so it's bound to spread to any place it can.

That said, I would totally buy a second hand mattress. People buy used clothes all the time, isn't that similar? Could contain anything (including bed bugs, the top ddg hits seem to suggest).