Patient with clinical and laboratory picture compatible with acute infectious mononucleosis with Epstein-Barr Virus (EBV). Although he still feels weak, his condition is slowly improving. There is a gradual disappearance of the fever episodes and rash, in parallel with gradual normalization of the liver enzymes results, and disappearance of atypical lymphocytes. The reactivation of Herpes labialis can be explained by the stress involved in the EBV infection or the Cortisone treatment.