Keywords: Cytomegalovirus (CMV); EBV - Epstein-Barr Virus; Herpes Simplex virus type 1 and type 2 (HSV-1/2); Human herpesvirus (HHV)-6; Human herpesvirus 7 (HHV-7); Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS); Serology; Varicela zoster virus (VZV).