Ask the experts
If a child had mono at the age of 14, would blood tests show up something now that would disqualify them from giving blood at 32 years of age?
No. A past history of mononucleosis does not disqualify a person as a blood donor. Blood for transfusion is not tested for the possibility of mononucleosis.
When a person has mono (infectious mononucleosis) there are changes in the blood reflecting the infection. Blood changes that go along with mono, in fact, led to the original discovery that mono is due to infection by a virus--the Epstein-Barr virus (EBV for short). A laboratory worker developed mono and was observed to develop antibodies directed against EBV. This case finding was followed by studies demonstrating that infectious mononucleosis was uniformly associated with the development of antibodies to EBV, thus establishing EBV as the cause of this long mysterious illness.
Infection with EBV is very, very common. Up to 70% of children have had mono (EBV) by age 4. In general, mono is a self-limited disease of relatively short duration. The small possibility of transmitting EBV through a blood transfusion is not considered at this time to be a significant health hazard.