The pathogens most frequently linked to ME/CFS are:
Certain enteroviruses:
- coxsackievirus B
- echovirus
Certain herpesviruses:
- Epstein-Barr virus
- cytomegalovirus
- HHV-6
Also:
- parvovirus B19
- Chlamydia pneumoniae (a bacterium which lives inside your cells)
We can now probably add
SARS-CoV-2 to the above list. And you can also include
Borrelia if you consider that chronic Lyme is a form of ME/CFS.
Very occasionally some cases of ME/CFS appear due to reactivated varicella zoster virus (you know if you have this because it causes a shingles rash).
These are the main pathogens that ME/CFS doctors will typically test you for.
There are a few other pathogens which are sometimes found in ME/CFS patients, as co-infections which may make the ME/CFS worse.