Infectious mononucleosis or “mono” is an illness that afflicts teenagers and young adults, mainly ages 14 to 30. It has been estimated that approximately 50 percent of students have had mono by the time they enroll in college. Mono is caused by the Epstein-Barr virus, a member of the Herpes family of viruses, but there are other viruses that may produce a mono-like illness. The disease usually occurs sporadically and outbreaks are rare. Many times the symptoms are so mild it isn't even recognized.
In underdeveloped countries, people are exposed to the virus in early childhood, when they aren't likely to develop noticeable symptoms. In developed countries such as the United States, the age of first exposure may be delayed until older childhood and young adulthood, when symptoms are more likely to occur.
The most common symptoms include excessive fatigue, headache, loss of appetite, sore throat, swelling of the tonsils, enlarged lymph nodes (swollen glands) in the neck, underarms, and groin. A low-grade fever occurs at first, and then rises to above 100 degrees after the third or fourth day. Sometimes, the liver and spleen are affected and enlarged. The disease lasts one to several weeks. A small proportion of affected people can take months to return to their normal energy level.
The Epstein-Barr virus is found in moist exhaled air and secretions from the nose and throat. It isn't as contagious as many other viruses but may be transmitted by direct contact, which explains the origin of mono's nickname as the “kissing disease.”
Symptoms appear from four to six weeks after exposure, but may be the same as many other illnesses, such as the common colds or strep throat. For this reason, it is particularly difficult to diagnose mono in the early stages of illness. The diagnosis is helped by two blood tests: one that looks at an increase in a specific type of white blood cell and another that identifies an antibody which is present when a person has mononucleosis.
No treatment other than rest is needed in the vast majority of affected people. Due to the risk of rupture of the spleen, contact sports should be avoided until clearance has been given by a physician. On rare occasions, a short-term course of steroids like prednisone may be of value for extreme throat swelling that inhibits swallowing or endangers breathing. Steroids don't cure the disease, but serve to reduce the inflammatory response. In most cases of mononucleosis, hospitalization isn't necessary.
Currently, there is no vaccine available to prevent infectious mononucleosis. People who have had mono can shed the virus periodically in their saliva for the rest of their lives.