Mononucleosis, or mono, is a contagious viral infection most commonly caused by the Epstein-Barr virus (EBV). Most babies and children exposed to the virus get only mild flu-like symptoms or no symptoms at all. But infection is usually more serious in teens and young adults. While the virus is most active, it causes symptoms and can easily spread to others. After symptoms ease, the virus stays in the body for life. It becomes mostly inactive. But it can become active again at times, often with no symptoms. At this point it can spread to others. This is especially true in people with a weak immune system.
The virus is usually spread through saliva, often by kissing, or by sharing food or eating utensils. It may also spread by breast milk, blood, or sexual contact. It takes about 4 to 6 weeks for symptoms to show up after exposure.
Early symptoms include headache, nausea, tiredness, and general muscle aching. This is followed by sore throat and fever. Lymph glands in the neck, under the arms, or in the groin may be swollen. Other symptoms include belly pain, reduced appetite, and skin rash. Symptoms usually go away in about 1 to 2 months. But they can last 4 months or longer.
In the first few days to weeks, the monospot blood test may be used to diagnose this disease. But that test may be negative even though you have the infection. Other blood tests are more accurate and may be done instead.
Mono can cause your spleen to swell. The spleen is a fist-sized organ in the upper left abdomen. It stores red blood cells and helps fight infections. Injury to a swollen spleen can cause the spleen to break open (rupture). This can cause life-threatening internal bleeding. To prevent this from happening, don't play contact sports or do strenuous activity for 8 weeks, or until your doctor says it's okay. A sharp blow or pressure to the area could rupture a swollen spleen.