Mononucleosis (mono) is an illness caused by a virus, which can result in fever, swollen lymph glands, and a sore throat
How Common Is Mononucleosis?
Mononucleosis is most common in people 10 to 35 years old, with its peak incidence in those 15 to 17 years old. Only 50 people out of 100,000 in the general population get mononucleosis, but it strikes as many as 2 out of 1,000 people in their teens and twenties, especially those in high school, college, and the military.
Two viruses can cause mononucleosis: the Epstein-Barr virus (EBV) and cytomegalovirus (CMV). Both viruses are in the herpes family, whose other members include viruses responsible for cold sores
. EBV causes mononucleosis in 85 percent of cases. When EBV is the cause, it is also referred to as infectious mononucleosis. When CMV causes it, it is also referred to as mononucleosis syndrome, or CMV mononucleosis.