Mononucleosis is a viral infection causing fevers, sore throat, and swollen lymph glands, especially in the neck. It is usually linked to the Epstein-Barr virus (EBV), but can also be caused by other organisms such as cytomegalovirus (CMV).

See also: Infectious mononucleosis (acute CMV infection)

Mononucleosis is often transmitted by saliva. While it is known as "the kissing disease," occurring most often in 15- to 17-year-olds, the infection may occur at any age.

Mono may begin slowly with fatigue, general ill feeling (malaise), headache, and sore throat. The sore throat slowly gets worse, often with swollen tonsils covered with a whitish-yellow covering. The lymph nodes in the neck are frequently swollen and painful.

A pink, measles-like rash can occur and is more likely if the patient is given ampicillin or amoxicillin for a throat infection. (Antibiotics should NOT be given without a positive strep test.) The symptoms of mono gradually go away on their own over a period of weeks to months.

• Fever
• Sore throat
• Swollen lymph nodes, especially in the neck and armpit
• General discomfort, uneasiness, or ill feeling
• Drowsiness
• Loss of appetite
• Muscle aches or stiffness
• Swollen 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
• Fatigue
• Nosebleed
• Hives

During a physical examination, the doctor may find swollen lymph nodes in the front and back of the neck, as well as swollen tonsils with the whitish covering. The doctor might also find a swollen liver or swollen spleen when pushing on your belly. There may be a skin rash.

Laboratory findings often include a higher-than-normal white blood cell count, and the characteristic finding of atypical lymphocytes -- unusual-appearing white blood cells that are seen when blood is examined under a microscope. Abnormal liver function tests are also characteristic.

Common tests for EBV include:

• A monospot test (positive for infectious mononucleosis)
• Epstein-Barr virus antigen by immunofluorescence (positive for EBV)
• Epstein-Barr virus antibody titers to help distinguish acute infection from past infection with EBV

Most patients recover within 2-4 weeks without medication. Younger children often don't have symptoms, while some older patients may have fatigue for up to 6 weeks.

There is no specific treatment available. Antiviral medications do not help. Steroid medication may be considered for patients with severe symptoms.

To relieve typical symptoms:

• Take acetaminophen or ibuprofen for pain and fever.
• Gargle with warm salt water for sore throat.
• Get plenty of rest. Drink plenty of fluids.
• Avoid contact sports while the spleen is swollen (to prevent it from rupturing).

The fever usually drops in 10 days, and swollen lymph glands and spleen heal in 4 weeks. Fatigue usually goes away within a few weeks, but may linger for 2 to 3 months.

• Secondary bacterial throat infection
• Rupture of spleen (this is rare; avoid pressure on the spleen)
• Neurological complications (these are rare, but include meningitis, seizures, ataxia, Guillain-Barre syndrome, and Bell's palsy)
• Hepatitis with jaundice (more common in patients older than 35)
• Hemolytic anemia
• Orchitis
• Death in immunocompromised individuals

The initial symptoms of mono feel very much like a typical viral illness. It is not necessary to contact a health care provider unless symptoms last longer than 10 days or you develop the following:

• Severe sore throat or swollen tonsils
• Difficulty breathing
• Abdominal pain
• Severe headache
• Persistent high fevers (more than 101.5°F)
• Yellow discoloration of your eyes or skin
• Weakness in the arm or legs

Call 911 or go to an emergency room if you develop:

• Sharp, sudden, severe abdominal pain
• Significant difficulty swallowing or breathing
• A stiff neck or severe weakness

The infection is probably spread by saliva and close contact. People may be contagious while they have symptoms and for up to a few months afterwards. The virus can live for several hours outside the body. Avoid kissing or sharing utensils if you or someone close to you has mono. The exact period that people are contagious varies.

Hoffman, R., ed. Hematology: Basic Principles and Practice. 4th ed. New York, NY: Churchill Livingstone, 2005.

Gershon, AA, Hotez, PJ, and Katz, SL, eds. Krugman’s Infectious Diseases of Children. 11th ed. St. Louis, Mo: Mosby; 2004.

Noble J, ed. Textbook of Primary Care Medicine. 3rd ed. St. Louis, Mo: Mosby; 2001.