well, maybe YOU never heard of this “mysterious shit”,but there’s papers going back to at least 1987 on post-viral inflammatory syndrome, not to mention 85,000,000 google hits:
https://www.google.com/search?q=post-viral+inflammatory+syndrome
I have heard of it, endlessly. Mysterious shit is great because it can be anything and do anything and nobody can gainsay it or argue about it. So yeah let’s add stupid mysterious shit to the evil covid. What the hell, we can be dealing with it for the rest of our lives...or until a Democrat is elected...Then I guarantee you won’t hear a damn thing about it.