The Epstein-Barr virus is the herpes virus responsible for mononucleosis. Most people have the human herpesvirus 4 at some point in life, according to the Centers for Disease Control. Saliva and other body fluids transmit the virus, and it remains active until the fluid dries.
The Epstein-Barr virus may result in diseases other than mono, including ear infections and diarrhea in children, Guillain-Barre syndrome, Burkitt's lymphoma, and nose or throat cancers, according to WebMD.
The symptoms of the virus take four to seven weeks to appear, and WebMD indicates that symptoms are often mild in children. In teens, the symptoms are more obvious and often include fatigue, fever, sore throat, swollen glands and a loss of appetite. Symptoms begin to clear in two to four weeks, although the teen often continues to experience fatigue for up to two months.
Because the symptoms of the virus are similar to those of other conditions, doctors sometimes use the Epstein-Barr virus test for diagnosis. This blood test checks for antibodies against the disease, according to MedlinePlus. If the test is negative, the doctor may order a subsequent one in about 10 days as it takes time for the body to develop the antibodies. The results of the test are also useful in determining if the infection is recent or from the past.