Dr. A. True Ott explains the terrain theory in detail.  This is key to understanding how "disease" actually forms in the body - whether it be cancer, heart disease, diabetes, or a supposed "virus infection."  Viruses and bacteria are an integral part of the human body - in fact, you can't survive with viruses and bacteria performing their duties in the human body.   Radiation in the form of Constant Wave (CW) communication microwaves most definitely causes mutations in  normally benign bacteria and parasites resulting in symptoms consistent with "COVID 19".