Mononucleosis-like disease may be caused by the cytomegalovirus (CMV) as well as the classic mononucleosis of the Epstein-Barr virus (EBV). Both viruses are members of the herpes virus family.

Mononucleosis caused by EBV is the most frequently encountered type and is responsible for approximately 85% of infectious mononucleosis cases. The infection is often transmitted by saliva. While peak incidence occurs in 15- to 17-year-olds, the infection may occur in any age, being most often diagnosed between the ages of 10 and 35.

Infectious mononucleosis may begin slowly with fatigue, malaise, headache, and sore throat. The sore throat becomes progressively worse, often with enlarged tonsils covered with a whitish-yellow fibrinous exudate. The lymph nodes in the neck are frequently enlarged and painful. A pink measles-like rash may occur in approximately 1 out of 10 individuals with mono.

Four out of five patients with mononucleosis who are given ampicillin or amoxicillin for their "throat infection" will develop the rash, but it is significantly darker and denser than the rash in those not given medication. Symptoms of mononucleosis gradually subside over a period of weeks to a month. The disease is generally self-limited.

Risk factors other than age are not known. The incidence in the United States is 2 out of 1,000 in adolescents and young adults. It is significantly lower for the entire U.S. population. Age of infection varies from country to country. For example, in Africa most individuals have been infected by age 3 years, an age at which there are very few symptoms.

Chronic EBV infection may be associated with some types of malignancy. In Africa, EBV is associated with Burkitt's lymphoma, while in China and among the Eskimos, EBV may be associated with cancers of the nose and throat (nasopharyngeal carcinoma). In organ transplant patients it can cause post-transplant lymphoproliferative disease (PTLD), a type of lymphoma.

• fever
• sore throat
• enlarged lymph nodes, especially in the neck and axilla (armpit)
• facial swelling
• general discomfort, uneasiness, or ill feeling (malaise)
• drowsiness
• loss of appetite
• muscle aches or stiffness
• enlarged spleen
• rash

Less frequently occurring symptoms include:

• jaundice (yellow cast to skin)
• headache
• neck stiffness
• sensitivity to light
• cough
• shortness of breath
• chest pain
• rapid heart rate
• irregular heart rate
• nosebleed
• hives
• fatigue

Common tests for EB include:

• a monospot test (positive for infectious mononucleosis)
• Epstein-Barr virus antigen by immunofluorescence (positive for EBV)
• a CBC
• • shows decreased platelet count
  • shows atypical lymphocytes
• a chemistry panel shows abnormal liver enzyme results

Other tests that may reflect changes:

• lymphocyte count (may become elevated)
• rheumatoid factor (may become temporarily positive)
• quantitative immunoglobulins (nephelometry)
• leukocyte alkaline phosphatase
• LDH isoenzymes
• LDH
• immunoelectrophoresis - serum
• febrile/cold agglutinins
• cryoglobulins
• Coombs' test, direct
• blood differential
• AST
• anti-smooth muscle antibody
• aldolase

Most patients recover within 4 to 6 weeks without medication. There is no specific treatment available. Antiviral medications do not help. Rest is needed, sometimes for a month or longer.

Relieve pain and fever with analgesics, and use warm salt water gargles for sore throat. A high protein, decreased fat diet and vitamin supplements may be recommended. Contact sports should be avoided while the spleen is enlarged.

Fever usually abates in 10 days, and swollen lymph glands and spleen heal in 4 weeks. Fatigue usually resolves within a few weeks, but may linger for 2 to 3 months.

• secondary throat infection
• rupture of spleen (rare) (avoid pressure on the spleen)
• neurological complications (rare)

Call for an appointment with your health care provider if symptoms indicate mononucleosis.

Go to the emergency room or call the local emergency number (such as 911) if a sharp, sudden pain in your left upper abdomen occurs. This could indicate a ruptured spleen, which requires emergency surgery.

Infectious mononucleosis can be contagious when in close or intimate contact with an infected person. Since the infection is probably spread by saliva, kissing or other transfer of oral secretions should be avoided.