My son has a virus, not mono, he has already had that. But the tip of his spleen was palpable. Dr said common with a virus. Agree?

CMV? Other? Your doctor is correct. True infectious mononucleosis is caused by Epstein Barr virus (EBV), but other viruses can cause mono-like illnesses with enlarged spleen. The most well known and perhaps most common is cytomegalovirus (CMV), but some cases are due to unknown viruses. Continue to follow-up with his doctor at least until his spleen returns to normal.