What nasty thing did you touch?
You know, if you could shine a special light that could illuminate cooties, if you pointed it at public doors, keypads etc, it would appear as though the surface was crawling, alive, millions of them moving, as they rapidly multiply.
If I had taken the whole dreaded “cooties” thing to heart, I could have avoided a whole lot of trouble. Damn... sometimes the warnings may be misdirected, but absolutely true.
There are such devices.