Infectious mononucleosis is a viral disease that affects certain types of white blood cells.
Most cases occur sporadically and outbreaks are rare. Infectious mononucleosis is not reportable in New York City. While most people are exposed to the Epstein-Barr virus at some point in their lives, very few go on to develop the symptoms of infectious mononucleosis. In underdeveloped countries, people are exposed in early childhood when they are less likely to develop symptoms. In developed countries, such as the United States, persons are usually not exposed until older childhood or young adulthood when symptoms are more likely to result.