Mononucleosis, or "mono," is a contagious viral illness caused by the Epstein Barr virus that initially attacks the lymph nodes in the neck and throat.


Mononucleosis is caused by the Epstein-Barr virus, a member of the herpes virus family. The disease develops if the virus is encountered for the first time at an age when the response of the body's immune system is most vigorous (that is, during adolescence and early adult life). The peak incidence of the illness occurs around the ages of 15 and 17.

Mononucleosis spreads by contact with moisture from the mouth and throat of a person who is infected with the virus. In addition to kissing; sharing drinking glasses, eating utensils, and toothbrushes, or touching anything that has been near the mouth of an infected person, may result in transmission of the disease.


Typically, the initial symptoms and signs of mono occur about 10 days after exposure in children and 30 to 50 days after exposure in adults. These symptoms include lack of energy, headache, fatigue, loss of appetite and chills.

After three to five days, any combination of the more intense symptoms and signs may become present, including:

  • severe sore throat

  • fever

  • swollen glands in the neck, armpits and groin

  • nausea

  • vomiting

  • upset stomach

  • enlarged spleen

  • enlarged liver

  • swollen eyelids

  • swelling around the eyes

  • rash

  • weight loss

  • drowsiness

  • muscle aches or stiffness

Less frequently occurring symptoms and signs include:

  • mild jaundice (a yellowish tint to skin)

  • neck stiffness

  • sensitivity to light/FONT

  • cough

  • shortness of breath

  • chest pain

  • rapid and/or irregular heart rate

  • nosebleeds

  • hives

Complications are rare and hospitalization is seldom required when they do occur. The most common complication is dehydration from not drinking enough fluids. Breathing may be obstructed by enlarged tonsils, adenoids and other lymph tissue in the back of the throat. On rare occasions, the enlarged spleen will rupture if the abdomen is hit or strained.

Additionally, the person may develop, hepatitis (inflammation of the liver), pericarditis (inflammation of the sac surrounding the heart), myocarditis (inflammation of the heart muscle), encephalitis (inflammation of the brain) or hemolytic anemia (destruction of the red blood cells).


The diagnosis is often obvious from the symptoms and examination of a blood smear, which shows many atypical lymphocytes (white blood cells).

There are two general types of blood tests for mono. The first is called a monospot test (or a spot test). Monospot relies on clumping of horse red blood cells by mononucleosis antibodies presumed to be in a person's serum. The other test is called the heterophil antibodies test. This test looks for antibodies (proteins produced by the immune system to counter the virus) that possess the unique ability to cause clumping of red cells taken from sheep's blood.

A physical examination sometimes reveals an enlarged liver and/or enlarged spleen, or the liver and spleen may simply be tender when gently pressed.


In most cases of mono, no specific treatment is necessary. The illness is usually self-limited and passes much the same way other common viral illness resolve. Doctors will, however, recommend bedrest and fluids. When the patient's temperature returns to normal, they should gradually resume normal activities as strength returns.

Tips for the care of individuals with mono:

  • For a fever and pain of swollen lymph glands: use acetaminophen or ibuprofen.

  • For a sore throat: drink milk shakes, fruit juices, and broths, and eat cool, bland foods. Additionally, gargle with saltwater and take aspirin.

    Note: If mono is accompanied by a streptococcal infection of the throat, an antibiotic will be prescribed to treat that condition. In severe cases, corticosteroid drugs that reduce swelling may be prescribed.

  • With an enlarged spleen: avoid contact sports for at least four weeks.

Most people recover in six to eight weeks, but in some cases take as long as six months for complete recovery. A tired feeling, which may include depression, is the last symptom to disappear. Mono may return in a milder form within a few months. Mono almost never reappears in full-blown form after a year.

It's generally wise to call the doctor if:

  • breathing becomes difficult or noisy

  • croup (an inflammation of the larynx accompanied by coughing, difficulty in breathing, fever, etc.) developes

  • abdominal pain occurs (especially high on the left)

  • skin becomes pale

  • bleeding into the skin occurs

  • swallowing becomes difficult

  • sleeping becomes very difficult

  • sinus or ear pain occurs

  • fever, still present after 10 days