EBV EA, or Epstein-Barr early antigen, is a protein complex within the Epstein-Barr virus (EBV), which causes infectious mononucleosis. Presence of antibodies to EBV EA can indicate active EBV infection for many, but not all people. At least two forms of EA have been identified. Diffuse EA (EA-D) is a 404-residue protein that functions as a processivity factor to the viral DNA polymerase. Restricted EA (EA-R) is 191 residues and acts as an apoptosis regulator, preventing the death of host cells.