Infectious Mononucleosis is a viral disease that affects certain blood cells. Other agents such as cytomegalovirus, toxoplasmosis, and human herpesvirus type 6, can cause an illness similar to mononucleosis. The disease usually occurs sporadically.
Outbreaks are rare.
While most people are exposed to the Epstein-Barr virus sometime in their lives, very few develop the symptoms of Infectious Mononucleosis. In underdeveloped countries, people are exposed in early childhood when they are not 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 result. For this reason, it is recognized more often in high school and college students. Symptoms include fever, sore throat, swollen glands, and feeling tired.