For SilverFox - Naturally occurring Chlorine dioxide?

I ran across a YT video recently and there was some person rambling-on on how Miracle-Mineral-Supplement can cure any flue and so I wanted to dial-in some of my own feedback on that. However, to my surprise, this same person claimed that chlorine dioxide ions or chlorine dioxide occurred in the human body naturally.

And so I wanted to ask if anyone(ie. SilverFox) had anything to offer on this? Because as far as I knew, my understanding was that Chlorine Dioxide was not a naturally occurring chemical.