Sorry, I made this private accidentally, reposting

Sorry, I made this private accidentally, reposting as a public reply..

I do dismiss the background mutation rate, in this instance. It's minor and incremental in a standard infection, from everything I've seen. Most "mutations" will, by definition, not result in any selective or competitive advantage.

Variants of Concern are the focus.. the immunocompromised are far and away the ideal hosts. There are highly studied cases where they have a sequential viral reference from when the patient first presented until their eventual death, often weeks or months later. The ebb and flow in a single host hones and allows beneficial mutations to arise and outcompete previous generations in a way that inter-host transmission, in more healthy hosts, doesn't. Coming in as wild type and leaving with 6+ significant, advantage conferring mutations does not happen in the course of standard infection. I've seen no evidence that suggests six sequential standard infections would confer similar.. quite the opposite.

There's lots of documentation on this.. not sure where your issue stems from.