Commonly called "mono," the disease is caused by the Epstein-Barr virus (EBV). Infection occurs by passing bodily fluids to another person as a result of coughing, sneezing and kissing. Hence, mononucleosis is often called the "kissing" disease.
This 10-year-old boy has mononucleosis too. Over the last week, he has complained of a worsening headache, difficulty swallowing, and not being able to drink enough fluids. He has a high fever and just doesn't feel well. His lips are also dry, a sign that he is dehydrated. His neck has swollen glands. During mononucleosis, we can often find an enlarged liver or spleen in the belly. Although this boy did not have this, there is clearly swelling of the tonsils inside his mouth. When we shine a light into his throat, we can see a whitish layer on his tonsils.