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Mononucleosis is a viral infection causing fever, sore throat, and swollen lymph glands, especially in the neck.

See also: Infectious mononucleosis (acute CMV infection)

Mono; Kissing disease

Mononucleosis, or mono, is often spread by saliva and close contact. It is known as "the kissing disease," and occurs most often in those age 15 to 17. However, the infection may develop at any age.

Mono is usually linked to the Epstein-Barr virus (EBV), but can also be caused by other organisms such as cytomegalovirus (CMV).

Mono may begin slowly with fatigue, a general ill feeling, headache, and sore throat. The sore throat slowly gets worse. Your tonsils become swollen and develop 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 you take the medicines ampicillin or amoxicillin for a throat infection. (Antibiotics should NOT be given without a positive Strep test.)

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

Less frequently occurring symptoms include:

• Chest pain
• Cough
• Fatigue
• Headache
• Hives
• Jaundice (yellow color to the skin)
• Neck stiffness
• Nosebleed
• Rapid heart rate
• Sensitivity to light
• Shortness of breath

During a physical examination, the doctor may find swollen lymph nodes in the front and back of your neck, as well as swollen tonsils with a whitish-yellow covering.

The doctor might also feel a swollen liver or swollen spleen when pushing on your belly. There may be a skin rash.

Blood work often reveals a higher-than-normal white blood cell (WBC) count and unusual-looking white blood cells called atypical lymphocytes, which are seen when blood is examined under a microscope. Atypical lymphocytes and abnormal liver function tests are a hallmark sign of the disease.

• A monospot test will be positive for infectious mononucleosis.
• A special test called an antibody titer can help your doctor distinguish a current (acute) EBV infection from one that occured in the past.

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.

• Death in persons with weakened immune systems
• Hemolytic anemia
• Hepatitis with jaundice (more common in patients older than 35)
• Inflammation of the testicles (orchitis)
• Neurological complications (rare), including:
  • Guillain-Barre syndrome
  • Meningitis
  • Seizures
  • Temporary facial paralysis (Bell's palsy)
  • Uncoordinated movements (ataxia)
• Secondary bacterial throat infection
• Spleen rupture (rare; avoid pressure on the spleen)

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:

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

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

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

Persons with mononucleosis may be contagious while they have symptoms and for up to a few months afterwards. How long someone with the disease is contagious varies. The virus can live for several hours outside the body. Avoid kissing or sharing utensils if you or someone close to you has mono.

Hurt C, Tammaro D. Diagnostic evaluation of mononucleosis-like illnesses. Am J Med. 2007 Oct;120(10):911.e1-8.

Jenson HB. Epstein-Barr Virus. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 251.