EGR1 and myalgic encephalomeyelitis/chronic fatigue syndrome: As EBI2 is a marker of EBV reactivation and as EGR1–3 are important for EBV reactivation in B lymphocytes (see below), these findings provide further support for the existence of an EBV-induced subtype of ME/CFS, and highlight, for the first time, the importance of a chronic immediate early gene response in EBV-associated ME/CFS.