I do research, but have also had ME/CFS since 1984 and Long Covid since 2022.

95% of the population is positive for EBV. Most people get it as children and it is mild. If you get it later, it can cause Mono.

If something lowers your immunity, EBV can reactivate and cause problems, but it is not the main causal agent.

The famous bubble boy who was born with no immune system died of EBV related cancers when he was given a bone marrow transplant from his sister who had a mild case of EBV in childhood. His body had no way to control EBV.

There are other newer viruses in the herpes family (HHV6A and HHV6B) that can also be reactivated in ME/CFS or Long Covid patients.

You can be tested for HHV6B at Quest labs, but not HHV6A. No one knows the prevalence of HHV6A virus since only specialty labs can test for it.
Research on ME/CFS can be found on the HHV-6 Foundation web site. https://hhv-6foundation.org/category/me-cfs