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Infectious Mononucleosis

(Epstein-Barr Virus [EBV] Infection; Mono)


Kenneth M. Kaye

, MD, Harvard Medical School

Reviewed/Revised Sep 2021 | Modified Sep 2022
Topic Resources

Epstein-Barr virus causes a number of diseases, including infectious mononucleosis.

Infection with the Epstein-Barr virus (EBV) is very common. EBV is a type of herpesvirus Overview of Herpesvirus Infections Some common viral infections are caused by herpesviruses. Eight different herpesviruses infect people: Three herpesviruses— herpes simplex virus type 1, herpes simplex virus type 2, and varicella-zoster... read more called herpesvirus 4. In the United States, about 50% of all children 5 years of age and nearly 95% of adults have had an EBV infection.

Most EBV infections cause no symptoms. Infectious mononucleosis typically develops in adolescents and young adults who are infected with EBV. Infectious mononucleosis is named for the large numbers of a certain type of white blood cell (mononuclear cells) in the bloodstream. Adolescents and young adults usually catch infectious mononucleosis by kissing someone infected with EBV.

After the initial infection, EBV, like other herpesviruses, remains in the body, mainly in white blood cells, for life. Infected people shed the virus periodically in their saliva. They can infect others during shedding, which causes no symptoms.

Symptoms of Infectious Mononucleosis

In most children younger than 5 years, the infection causes no symptoms. In adolescents and adults, it may or may not cause infectious mononucleosis.

The usual time between infection and the appearance of symptoms is thought to be 30 to 50 days. This interval is called the incubation period.

The four main symptoms of EBV infectious mononucleosis are

Not everyone has all four symptoms. Usually, the infection begins with a general feeling of illness (malaise) and low grade fever followed by sore throat and/or swollen lymph nodes. Fatigue is often severe and is usually most severe during the first 2 to 3 weeks but may last for months. The fever usually peaks at about 103° F (about 39.5° C) in the afternoon or early evening. The throat is often very sore, and puslike material may be present at the back of the throat. Most commonly, the lymph nodes of the neck are swollen, but any lymph node may be swollen. In some people, the only symptom is swollen lymph nodes (sometimes mistakenly called "swollen glands").

The spleen is enlarged in about 50% of people with infectious mononucleosis. In most infected people, an enlarged spleen causes few if any symptoms, but it may rupture, particularly if injured. Rupture of the spleen Spleen Injury Because of the spleen’s position in the upper left side of the abdomen, a severe blow to the stomach area can damage the spleen, tearing its covering, the tissue inside, or both. An injured... read more is life threatening. The liver may also enlarge slightly. Sometimes the area around the eyes is swollen.

Rashes develop infrequently. However, people with an EBV infection who take the antibiotic ampicillin may be more likely to develop a rash.

How long symptoms last varies. After about 2 weeks, symptoms subside, and most people can resume their usual activities. However, fatigue may persist for several more weeks and, occasionally, for months. Fewer than 1% of people die, usually because of complications such as encephalitis, rupture of the spleen, or blockage of the airways.

Diagnosis of Infectious Mononucleosis

  • A blood test

The symptoms of infectious mononucleosis also occur in many other viral and bacterial infections. Therefore, infectious mononucleosis is often unrecognized. However, swollen lymph nodes Swollen Lymph Nodes Lymph nodes are tiny, bean-shaped organs that filter lymph fluid. They are located throughout the body, but particular collections are found just under the skin in the neck, under the arms,... read more Swollen Lymph Nodes , particularly in the neck, strongly suggest infectious mononucleosis.

Usually, a simple blood test known as a heterophile antibody or monospot test is done to confirm the diagnosis. This test can sometimes be negative early in illness in adolescents and adults, and if doctors strongly suspect the infection, they can repeat the test about a week later. This test is much less reliable and often negative in young children with infectious mononucleosis. An alternative test to confirm the diagnosis is a specific antibody blood test for EBV. (Antibodies Antibodies One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more Antibodies are produced by the immune system to defend against a particular attacker, such as EBV.)

Often, a complete blood count is also done. Finding many characteristic mononuclear white blood cells (atypical lymphocytes) may be the first clue that the diagnosis is infectious mononucleosis.

Treatment of Infectious Mononucleosis

  • Initially rest

  • Pain relievers

  • Sometimes corticosteroids for certain complications

There is no specific treatment.

People with infectious mononucleosis are encouraged to rest during the first week or two, while symptoms are severe. After about 2 weeks, they may be more active. However, because of the risk of rupturing the spleen, heavy lifting and contact sports should be avoided for at least 1 month, until doctors confirm by examination or sometimes ultrasonography that the spleen has returned to normal size.

Acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs, such as aspirin or ibuprofen) can relieve fever and pain. However, aspirin should not be given to children because of the small risk that it may cause Reye syndrome Reye Syndrome Reye syndrome is a very rare but life-threatening disorder that causes inflammation and swelling of the brain and impairment and loss of function of the liver. The cause of Reye syndrome is... read more , which can be fatal.

Some complications, such as severe swelling of the airways, may be treated with corticosteroids.

Currently available antiviral drugs have little effect on the symptoms of infectious mononucleosis and should not be used.

Drugs Mentioned In This Article

Generic Name Select Brand Names
7T Gummy ES, Acephen, Aceta, Actamin, Adult Pain Relief, Anacin Aspirin Free, Apra, Children's Acetaminophen, Children's Pain & Fever , Comtrex Sore Throat Relief, ED-APAP, ElixSure Fever/Pain, Feverall, Genapap, Genebs, Goody's Back & Body Pain, Infantaire, Infants' Acetaminophen, LIQUID PAIN RELIEF, Little Fevers, Little Remedies Infant Fever + Pain Reliever, Mapap, Mapap Arthritis Pain, Mapap Infants, Mapap Junior, M-PAP, Nortemp, Ofirmev, Pain & Fever , Pain and Fever , PAIN RELIEF , PAIN RELIEF Extra Strength, Panadol, PediaCare Children's Fever Reducer/Pain Reliever, PediaCare Children's Smooth Metls Fever Reducer/Pain Reliever, PediaCare Infant's Fever Reducer/Pain Reliever, Pediaphen, PHARBETOL, Plus PHARMA, Q-Pap, Q-Pap Extra Strength, Silapap, Triaminic Fever Reducer and Pain Reliever, Triaminic Infant Fever Reducer and Pain Reliever, Tylenol, Tylenol 8 Hour, Tylenol 8 Hour Arthritis Pain, Tylenol 8 Hour Muscle Aches & Pain, Tylenol Arthritis Pain, Tylenol Children's, Tylenol Children's Pain+Fever, Tylenol CrushableTablet, Tylenol Extra Strength, Tylenol Infants', Tylenol Infants Pain + Fever, Tylenol Junior Strength, Tylenol Pain + Fever, Tylenol Regular Strength, Tylenol Sore Throat, XS No Aspirin, XS Pain Reliever
Anacin Adult Low Strength, Aspergum, Aspir-Low, Aspirtab , Aspir-Trin , Bayer Advanced Aspirin, Bayer Aspirin, Bayer Aspirin Extra Strength, Bayer Aspirin Plus, Bayer Aspirin Regimen, Bayer Children's Aspirin, Bayer Extra Strength, Bayer Extra Strength Plus, Bayer Genuine Aspirin, Bayer Low Dose Aspirin Regimen, Bayer Womens Aspirin , BeneHealth Aspirin, Bufferin, Bufferin Extra Strength, Bufferin Low Dose, DURLAZA, Easprin , Ecotrin, Ecotrin Low Strength, Genacote, Halfprin, MiniPrin, St. Joseph Adult Low Strength, St. Joseph Aspirin, VAZALORE, Zero Order Release Aspirin, ZORprin
Advil, Advil Children's, Advil Children's Fever, Advil Infants', Advil Junior Strength, Advil Migraine, Caldolor, Children's Ibuprofen, ElixSure IB, Genpril , Ibren , IBU, Midol, Midol Cramps and Body Aches, Motrin, Motrin Children's, Motrin IB, Motrin Infants', Motrin Junior Strength, Motrin Migraine Pain, PediaCare Children's Pain Reliever/Fever Reducer IB, PediaCare Infants' Pain Reliever/Fever Reducer IB, Samson-8
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