Hi! Thank you for consulting with Healthcare Magic! Infectious Mononucleosis is caused by a virus (Epstein Barr Virus). Among children, transmission may occur when there s exchange of saliva such as when they share water bottles. The symptoms are fever, sore throat, fatigue and generalized lymphadenopathy- which means enlarged lymph nodes. Patients may also complain of headache and body pain like in other viral infections. On examination, there s enlargement of the spleen and liver such as that seen in your son. Did your doctor do any test to confirm that its Infectious Mononucleosis? Although the symptoms are pointing at it. There s no specific treatment for this. Its mostly supportive, fever medicine and rest. It is best for your child to avoid strenuous activities in the next 2-3 weeks while splenomegaly is still present. We want to avoid any trauma that can cause the spleen to rupture. Hope I was able to help you. Have a good day! Sincerely, Hannalae Dulay-See, M.D.