My personal paranoia story:
Every day the mailman drops a letter into my mailbox. I think to myself, "I wonder how many people have touched that letter?" So I take the letter out of the mailbox, and drop it on the floor just inside my front entry, then go disinfect my hands. That's where the letters sat for several days while I pondered what to do with them.
So today, I set the oven to 250° F, and got out a baking sheet, piled the letters onto the sheet and put them into the oven. I let them bake for a couple of hours. Took them out to cool down and then opened them. If I'm dead in a couple of weeks, then I guess it didn't work.
I wouldn't recommend this for plastic parts, but there's always boiling water.