Symptoms of  Infectious Mononucleosis:

The most prominent symptoms of mononucleosis are weakness and fatigue. Some other common symptoms include:

• Sore throat and/or swollen tonsils
• Fever and chills
• Nausea and vomiting
• Decreased appetite
• Swollen lymph nodes in the neck and armpits
• Headaches or joint pain
• Enlarged spleen
• Jaundice
• Skin rash

Serious complications of mononucleosis include an enlarged spleen or inflamed liver. In rare cases, the spleen may rupture (break open), producing sharp pains on the left side of the abdomen. This symptom calls for immediate medical attention. Other symptoms of a ruptured spleen include light-headedness, rapid heartbeat, and difficulty breathing. Other rare complications include damage to the heart, brain, or the body's red blood cells.

Symptoms usually do not appear until four to seven weeks after exposure to  Epstein-Barr virus (EBV). Even though symptoms have not appeared, an infected person is still contagious. That is, he or she can pass the disease on to another person. An infected person remains contagious for up to five months after symptoms have disappeared.  People can live in close contact with an infected person without catching the disease as long as they do not have direct contact with that person's saliva.