What Is It?
Infectious mononucleosis is an illness caused by a viral infection. It is commonly called mononucleosis, or "mono." Mononucleosis is most often caused by the Epstein-Barr virus. In some cases, it is caused by other viruses.
Mononucleosis has been nicknamed the "kissing disease." This is because Epstein-Barr virus commonly is transmitted during kissing. However, sneezes and coughs also can transmit the virus.