Herpesviruses may or may not be causal in ME/CFS, but chronic (active or frequently reactivating) infection could easily be the cause of many of our symptoms. They can also affect immune function.
We have suffered for many years from the assumption on the part of medical authorities that herpesviruses cannot be chronic -- that our immune systems handle it. Herpesvirus test interpretation is colored by assumptions based on healthy people, ie that a high IGG titre only indicates a past infection. That assumption collapses if the patient has immune dysfunction. Since doctors are working under the assumption that only transplant patients and HIV patients have immune dysfunction, and ME/CFS patients are neither, our high titres don't mean anything -- according to their assumptions. Deadly wrong assumptions, it's beginning to appear.
Clinical evidence is showing substantial improvement in functionality (in a subset of ME/CFS patients) with antiherpetic medications (Valcyte, Valtrex, Famvir). This suggests that herpesviruses may play a part in our illness, so testing for them seems like a smart move to me. Also, since herpesviruses can go latent and reactivate, testing at the wrong time could easily miss reactivations leading to the false conclusion that the patient is not struggling with active herpesvirus infections. Testing at multiple time points might show up a frequent reactivation pattern.
It's too bad that they aren't also testing for HSV-1 (HHV1) and herpes zoster/chicken pox (HHV3). It's an economy thing, I suppose. The infections most noticed so far in ME/CFS patients are EBV (HHV4), CMV(HHV5), and HHV6, so I guess they're focusing on those for now.
Proving that a large subset of ME/CFS patients in the UK are suffering from chronic/reactivating herpesvirus infections could lead to the availability of antiherpetic meds under the NHS. That could be huge for UK patients --and helpful for patients worldwide as well.