<b>Overview</b> Mononucleosis is a respiratory virus that affects the blood cells and salivary glands (glands responsible for producing saliva). Even though anyone can get mononucleosis, most people who get the illness are between the ages of 15 and 25.

Mononucleosis is an illness caused by the Epstein-Barr virus. Mononucleosis is referred to as the kissing disease because it can spread easily, especially through close personal contact. Mononucleosis has flu-like symptoms and can make you feel very ill.

Commonly referred to as the kissing disease, mononucleosis—or mono—can spread in a variety of ways, not just through kissing. The condition is caused by the Epstein-Barr virus and mainly affects adolescents or young adults, according to the Mayo Clinic.

Mononucleosis is a viral infection caused by the Epstein Barr virus. It is spread through saliva and symptoms may include sore throat, fever, fatigue, weight loss and loss of appetite. It typically lasts for two or three weeks, but it can persist past this time.