Medically Reviewed By William C. Lloyd III, MD, FACS

What is mononucleosis?

Mononucleosis is an infectious condition caused by the Epstein-Barr virus (EBV), which is part of the herpesvirus family. It is one of the most common viruses and will infect most people at some point in their lives. In the United States, nearly 95% of adults between the ages of 35 and 40 years have been infected with EBV (Source: CDC Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source ).

Mononucleosis produces flu-like symptoms, including fatigue, fever, a painful sore throat, aches and pains, and headache. Infectious mononucleosis can also cause swelling of the lymph nodes, the spleen, and the liver. People who have already been infected with the virus typically do not get the disease again, although the virus itself survives forever within cells. The fever and sore throat commonly resolve on their own within 10 days. If your spleen or lymph nodes have become enlarged, the enlargement may persist for up to four weeks. In some cases, fatigue may last for a few months following the illness.

Even though the symptoms of EBV resolve, the virus remains in your body indefinitely and may be present in your saliva. Reactivation of the virus is far less common than other herpes viruses. It can occur at any time, but this does not result in any symptoms. You may be able to spread the infection to others while you are ill or while you are experiencing a symptom-free reactivation of the virus.

Seek prompt medical care if you are being treated for mononucleosis and experience symptoms lasting longer than 10 days, or if you have symptoms that include abdominal pain, difficulty breathing, high fever (higher than 101 degrees Fahrenheit), severe headache, severe sore throat or swollen tonsils, muscle weakness, or yellowing of the skin or the whites of the eyes.

What are the symptoms of mononucleosis?

Symptoms of mononucleosis resemble those of influenza (flu) and include fever, sore throat, aches and pain, cough, and swollen lymph nodes. Typically, symptoms do not last for more than four months.

Common symptoms of mononucleosis

Symptoms and signs of mononucleosis generally resemble those of the flu and include:

Less common symptoms of mononucleosis

In some cases, other signs and symptoms may occur along with mononucleosis. These can include:

  • Enlarged spleen or liver
  • Headache
  • Hives
  • Rapid heart rate (tachycardia)
  • Stiff neck
  • Yellowing of the skin and whites of the eyes (jaundice)

Symptoms that might indicate a serious condition

Although the symptoms of mononucleosis resemble the flu and generally resolve on their own, seek immediate medical care (call 911) if you, or someone you are with, have any of these serious symptoms including:

  • Abdominal pain
  • Difficulty breathing
  • Neck stiffness
  • Persistent high fever (higher than 101 degrees Fahrenheit)
  • Severe headache
  • Severe sore throat or swollen tonsils
  • Weakness in the arm or legs
  • Yellowing of the skin or the whites of the eyes

What causes mononucleosis?

Infectious mononucleosis is caused by infection with the Epstein-Barr virus (EBV). It is transmitted through saliva from one person to another, hence its nickname, “kissing disease.” When you are exposed to the virus, your immune system will develop antibodies and launch an immune reaction, producing the associated flu-like symptoms. Symptoms may appear up to four to six weeks after infection.

People with the infectious form of the disease can transmit it to others, but isolation is not necessary, since many healthy people carry the virus in their saliva.

What are the risk factors for mononucleosis?

Some factors increase the risk of developing mononucleosis. Not all people with risk factors will get mononucleosis. Risk factors for mononucleosis include:

  • Contact with saliva from an infected person
  • Other forms of exposure to contagious persons

Reducing your risk of mononucleosis

You can reduce your risk of developing mononucleosis infection by:

  • Avoiding contact with a contagious person
  • Avoiding saliva exchange with an infected person

How is mononucleosis treated?

Treatment of mononucleosis begins with seeking medical care from your health care provider. To determine if you are infected, your health care provider will ask you to provide blood samples for laboratory testing, which will determine the number of white blood cells in your body. A “mono spot” test may be performed as a rapid test to determine whether you have antibodies to the Epstein-Barr virus.

Although there is no cure for the viral infection, the symptoms of mononucleosis may be treated in a manner similar to those of the flu, with bed rest and fluids.

Treatments for mononucleosis

Treatments for mononucleosis are directed at relieving your symptoms and include:

  • Bed rest

  • Hydration with plenty of fluids

  • Pain-relieving medications such as ibuprofen (Motrin, Advil) or acetaminophen (Tylenol)

What you can do to improve your mononucleosis

In addition to following your health care provider’s instructions and taking all medications as prescribed, you can help alleviate your symptoms and decrease your risk of complications by:

  • Avoiding contact sports until your health care provider allows, if you have an enlarged spleen, to avoid risk of splenic rupture

  • Gargling with warm saltwater to relieve throat pain

  • Getting plenty of rest

  • Using over-the-counter throat lozenges

What are the potential complications of mononucleosis?

Symptoms of mononucleosis seldom last for more than four months, but in some cases they may become chronic, lasting for more than six months. In this case, you may be evaluated by your doctor to determine whether you may have chronic fatigue syndrome.

Mononucleosis can produce serious complications including:

  • Hepatitis with yellowing of the skin and whites of the eyes (jaundice)

  • Orchitis (inflammation of the testes)

  • Spleen rupture (rare; avoid pressure on the spleen)

  • Thrombocytopenia (low platelet levels; platelets help form clots to stop blood loss)

Neurological complications of mononucleosis are rare. They include:

Was this helpful?
  1. Epstein-Barr virus and infectious mononucleosis. Centers for Disease Control and Prevention.
  2. Mononucleosis. Medline Plus, a service of the National Library of Medicine National Institutes of Health.
  3. Collins RD. Differential Diagnosis in Primary Care, 5th ed. Philadelphia: Lippincott, Williams & Williams, 2012.
  4. Feigin RD, Cherry JD, Demmler-Harrison GJ, Kaplan SL (Eds), Textbook of Pediatric Infectious Diseases, 6th ed. Philadelphia: Saunders, 2009.
  5. Luzuriaga K, Sullivan JL. Infectious mononucleosis. N Engl J Med 2010; 362:1993.
Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jan 18
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