Infectious Mononucleosis

Infectious mononucleosis (“mono”) is an infection that causes sore throat, fever, swollen glands, and tiredness or fatigue.

Infectious mononucleosis is transmitted by exposure to saliva, so it can be spread by kissing, by sharing glasses or cutlery, and by droplets spread by coughing. Mono is usually caused by the Epstein-Barr virus. It most often affects children, teenagers, and young adults.

Other diseases that cause similar symptoms include infection with other viruses that cause sore throat, streptococcal bacteria (“strep throat”), or cytomegalovirus.

Most patients with mono have a sore throat, fever, and headache and feel tired or fatigued. Most also have swollen glands in the neck, behind the ears, and even toward the back of the head. Some also have pus on the tonsils and small red dots on the roof of the mouth.

A doctor may order a blood test to help diagnose mono. He or she may look for certain kinds of white blood cells called lymphocytes. Patients with mono may have high levels of lymphocytes in their blood, especially forms of these cells called atypical lymphocytes. Lymphocytes are not dangerous and are produced by the body to help fight infection. A doctor may also order a test for the antibodies that the lymphocytes make to fight the infection, often called a monospot test. Because it takes your body time to make these antibodies, the results of these tests are sometimes normal in patients who actually do have mono, especially during the first week or so of their infection.

Treatment for mono consists mainly of rest. Patients can take medicine such as acetaminophen, ibuprofen, or naproxen for fever and body aches. Aspirin should be avoided in children because it is associated with Reye syndrome. Corticosteroids are sometimes prescribed in severe cases or in patients with complications. Patients should get as much rest as they need, but being confined to bed is not necessary and does not improve outcomes. Antibiotics do not help unless the patient has also had a positive test result for strep throat. Many patients with mono have an enlarged spleen, which is part of their body’s response to the infection. Because an enlarged spleen is more likely to rupture, patients with mono should avoid contact sports and activities that could result in blows to the abdomen until they have recovered. It may take 3 months or more to completely recover from mono.

Conflict of Interest Disclosures: The author has completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Sources: Ebell MK, Call M, Shinholser J, Gardner J. Does this patient have infectious mononucleosis? The Rational Clinical Examination Systematic Review. JAMA. doi: 10.1001/jama.2016.2111.

Ebell MH. Epstein-Barr virus infectious mononucleosis. Am Fam Physician. 2004;70(7):1279-1287.

Womack J, Jimenez M. Common questions about infectious mononucleosis. Am Fam Physician. 2015;91(6):372-376.

Topic: Infectious Diseases