Mononucleosis is an infectious disease of the lymphatic system, the liver and the respiratory system. This means the bronchi, the throat, the spleen and lymph nodes are affected. Mononucleosis usually strikes children and young adults.
Mononucleosis, or mono is mostly caused by the Epstein-Barr virus, or EBV. EBV is a type of herpes virus. It is so widespread that nearly every adult has it, though most people will not come down with mononucleosis. There is also another member of the herpes family, which can cause mononucleosis.