I have seen very little info about the method used, it's some new tech that can supposedly detect infections anywhere in the body, based on finding the DNA of pathogen in the blood. Ron Davis talks about it at timecode 25:50 in
this presentation.
From his description of the method, it does not seem likely it would detect partially reactivated latent infections, nor abortive infections, though that's just my guess, I don't know for sure.
Dr Chia is saying we need to test tissue samples to detect the infections in ME/CFS, as the infections are hiding in the tissues, likely as intracellular infections.
There are lots of studies that have found enterovirus in ME/CFS tissue biopsies, but there are almost no studies that have looked for herpesviruses in the tissues. So we have direct evidence for the presence of enterovirus infection in ME/CFS, but we do not have this evidence for herpesvirus. The evidence for herpesvirus comes more from chronically raised IgG levels in ME/CFS, which suggest a herpesvirus infection is going on somewhere in the body.
But we have not pinpointed the locations of the herpesvirus infection, as we have with enterovirus. With enterovirus we know these infections are found in the muscles, gut and brains of ME/CFS patients.