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Patient education: Infectious mononucleosis (mono) in adults and adolescents (Beyond the Basics)

Paul G Auwaerter, MD, MBA, FIDSA
Section Editors
Martin S Hirsch, MD
Sheldon L Kaplan, MD
Deputy Editor
Jennifer Mitty, MD, MPH
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Infectious mononucleosis, also known as mono or the "kissing disease," is an infection that may cause fever, sore throat, fatigue, and/or enlarged lymph nodes in the neck. It most commonly occurs in adolescents and young adults. Although not generally considered a serious illness, mononucleosis can lead to significant loss of time from school or work due to profound fatigue.

This topic will discuss the symptoms, diagnosis, and treatment of mononucleosis in adolescents and adults.


Mono is caused by acquiring Epstein-Barr virus (EBV), which can spread from person to person through contact with saliva. Thus, a person can be exposed to the virus by kissing, sharing eating utensils, or drinking from the same glass as a person who has mono.

Many people are exposed to EBV at some point during childhood, although they may not realize it at the time. For adolescents and young adults who were not infected as a child, exposure can still result from contact with an infected person's saliva. In addition, it may also be possible for them to be exposed to the virus through contact with other bodily fluids, such as semen or vaginal secretions.


Most young children who become infected with Epstein-Barr virus (EBV) do not develop symptoms. In contrast, people who are first exposed to EBV as adolescents or adults are more likely to develop symptomatic infection; this is due to the way their immune systems respond to the virus. (See "Clinical manifestations and treatment of Epstein-Barr virus infection".)

Common symptoms — It may take four to eight weeks after exposure to the virus for the first symptoms (body aches, headache, low-grade fever) to appear. The most common mono symptoms include:

Fever (temperature greater than 100.4ºF or 38ºC)

Sore throat

Enlarged lymph nodes (glands) in the neck

Fatigue, which may be severe and can occasionally last for more than a month

Some people have all of these symptoms while others have only one or two symptoms, such as sore throat or fever and enlarged lymph nodes. Young children and older adults may have only a fever and muscle aches. (See "Infectious mononucleosis in adults and adolescents".)

Enlargement of the spleen — The spleen is an organ in the left upper abdomen, just under the diaphragm (figure 1). It becomes enlarged in about half of people with mono. If the spleen becomes enlarged, doctors recommend avoiding contact sports or heavy lifting for a few weeks. This advice is given to avoid the rare complication of splenic rupture that can occur after trauma, but can also happen spontaneously. Symptoms of rupture include sudden, sharp pain in the abdomen. This is a potentially life-threatening complication that requires immediate medical treatment. (See 'When can I go back to work or school?' below.)


Mono may be suspected based upon a person's symptoms and physical examination. Blood tests are done to confirm the diagnosis. However, the most commonly used blood test for diagnosis in North America, known as the Monospot, can be falsely negative during the first weeks of symptoms.


The goal of mono treatment is to ease the symptoms while the immune system contains the virus. Antibiotics are not helpful because mono is caused by a virus, and there are no antiviral medications that are known to effectively treat or cure Epstein-Barr virus.

Pain and fever — Sore throat, muscle aches, and fever can be treated with non-prescription medications, such as acetaminophen (sample brand name: Tylenol) or ibuprofen (sample brand names: Motrin, Advil). Acetaminophen is broken down by the liver. Thus, it is important to closely follow the dosing instructions or your healthcare provider's instructions to safely take this medication. Acetaminophen and ibuprofen are also recommended for use in children. Aspirin should not be given to young children with mono because of possible liver complications.

Rest — Mono can cause severe fatigue, although most people recover within two to four weeks. For some, significant tiredness lasts for weeks to months. Early in the infection, it is important to get adequate rest, although complete bed rest is not necessary.

Diet — Feeling ill often causes a loss of appetite. This is normal, and usually improves as the infection improves. It is important, even if you have no appetite, to drink an adequate amount of fluids. This is especially true if you are taking ibuprofen for pain or fever because ibuprofen can affect kidney function if you become dehydrated. You are drinking adequate fluids if your urine is a pale yellow color.


Many people with mono develop an enlarged spleen, which can last for a few weeks or longer. Although you can return to school or work when you are feeling better, it's important to avoid activities that can cause injury to the spleen.

Experts generally recommend that athletes not participate in contact or vigorous sport activities for at least the first three to four weeks of the illness. Your healthcare provider should determine when it is safe for you to participate in strenuous activities or contact sports.

When you do begin participating in sports activities again, we recommend starting slowly, increasing activity gradually. Even highly trained athletes may not feel as fit after having mono as they did before the illness.


Most people who suffer with mono recover completely without any long-term complications. Symptoms usually begin to improve within one to two weeks.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Mononucleosis (The Basics)
Patient education: Swollen neck nodes in children (The Basics)
Patient education: Cytomegalovirus (The Basics)
Patient education: When to worry about a fever in adults (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

This topic currently has no corresponding Basic content.

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Clinical manifestations and treatment of Epstein-Barr virus infection
Overview of diagnostic tests for cytomegalovirus infection
Epidemiology, clinical manifestations, and treatment of cytomegalovirus infection in immunocompetent adults
Evaluation of acute pharyngitis in adults
Infectious mononucleosis in adults and adolescents

Literature review current through: Nov 2017. | This topic last updated: Mon Jul 10 00:00:00 GMT+00:00 2017.
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