Thank you for your comment. Koch’s postulates are not perfect and do not apply to some infections (e.g., Plasmodium falciparum parasite, herpes simplex virus, and even some bacteria). I received a similar comment about the SARS-CoV-2 purification or isolation in a PCR article I wrote a while back, and here is my response to the comment that might interest you:

Thanks for your comment.

And here’s a friend link to the PCR article, if you are interested:

Is the Coronavirus PCR Test a Fraud? An Objective Look Into Why People Insist So