It possible to be relapsing with mono and not show any obvious symptoms? blood tests would be abnormal?

Not likely relapse.: Infectious mononucleosis has 2 big causes. Cytomegalovirus (cmv), and epstein-barr virus (ebv). CMV has high fevers with chills, fatigue, and malaise. The main lab finding is peripheral lymphocytosis with over 10% atypical lymphocytes on blood smear. Ebv has pharyngitis and cervical lymphadenopathy. In both cases, infants may be asymptomatic or show mild diseaese, though CMV has side effects.