I had lots of testing for viruses (30 years ago), like CMV (negative), EBV (positive antibodies -showing past infection like a large proportion of the population), HIV (negative)and a Mantoux test for TB (negative) Hepatitis A, B and C (negative and showed vaccination status), possibly a few others, ?japanese encephalitis, I forget.
It was as thorough as my GP and Infectious Disease Physician, could be at the time, and never had any other infection testing despite having some nice rashes that surprised my GP (still get them occasionally) erythema multiforme, they responded to antihistamines, very quickly, so put down as “mast cell activation”, even if it was viral persistence or whatever immune mediated process there was no antiviral or good treatment they would have given me, as not a lot is funded here in the public service.
But I am seeing the same specialist at my hospital, in a few months so be interested to see what he has to say about how my health has deteriorated so much with ME/CFS and got no support or treatment other than my own reading…
I don’t think I had Lyme testing, we don’t have the tics here that carry the bacteria (but had done a lot of travel) and had work exposure to some infectious disease, but most of those infections have very clear associated symptoms and signs.
So basically I hope they find a cause for you, but yes, having low expectations means if they do find something, it will be hopefully be something they have an effective treatment for.