What Is Mononucleosis (Mono)?

In This Article
View All
In This Article

Infectious mononucleosis, or mono, is an infection caused by viruses—usually the Epstein-Barr virus (EBV). Mono can affect people of all ages, but it's most commonly seen in teenagers and young adults. The virus is highly contagious and is sometimes called the “kissing disease” because it usually is spread through saliva. 

Common mono symptoms include fatigue, fever, swollen lymph nodes, and sore throat. Mono is diagnosed through a physical exam and blood tests. Treatment usually involves rest and pain relievers, but medications are sometimes needed for more serious cases. In the United States, about 125,000 mono cases are reported annually.


Mono symptoms develop slowly and usually appear within four to six weeks of exposure to the Epstein-Barr virus (EBV). Symptoms range from mild to severe, though many people infected with EBV have no symptoms—especially young children.

When mono symptoms develop, they typically last 2 to 3 weeks, though fatigue can persist for months after the infection. Classic mono symptoms include:

  • Extreme fatigue 
  • Fever
  • Sore throat
  • Swollen lymph nodes, especially in the neck and armpits 

Less common mono symptoms include:

  • Swollen spleen or liver
  • Rash 
  • Headache 
  • Body aches
  • Loss of appetite 

What Causes Mono? 

The Epstein-Barr virus (a type of herpes virus) causes about 90% of mono cases, but other viruses can cause it, too. EBV spreads through close contact with another person’s saliva or bodily fluids (e.g., kissing, sharing utensils, sexual contact). 

Once the virus enters the body, it infects and alters certain white blood cells—called B lymphocytes—causing them to divide and rapidly multiply. The immune system produces T lymphocytes and other immune cells to fight the EBV-infected B lymphocytes, which can lead to mono symptoms.

Risk Factors

By age 30, about 90% of the world’s population has EBV antibodies, meaning they had an infection at some point. Once infected, EBV remains in the body for life but does not cause long-term problems for most people.

Not everyone exposed to EBV will develop mono. Certain risk factors can increase the likelihood of developing it:

  • Age (adolescents and young adults aged 15-24) 
  • Living in crowded spaces (e.g., college dorms) 
  • Sharing personal items (e.g., utensils, cups) 
  • Low socioeconomic status 
  • Weakened immune system
  • Having multiple sex partners

How Is Mono Diagnosed?  

Diagnosing mono involves a physical exam, a review of symptoms, and a blood test. 

During the physical exam, a healthcare provider will ask about your symptoms, including when they started and how severe they are. They will touch your neck and throat to look for swollen lymph nodes and palpate your abdomen to check for a swollen liver or spleen.

They may order blood tests to confirm the diagnosis if mono is suspected. Blood tests used to diagnose mono include:

  • Monospot test: This test detects antibodies in the blood that indicate a current or recent infection. Monospot can produce false negatives, especially early in the illness, so you may be tested again a week later to confirm a diagnosis. False positives are also possible because the test detects antibodies for several conditions, not just mono. 
  • EBV antibody test: This test looks for Epstein-Barr virus antibodies in the blood. If the results are positive, it means you have the virus. 
  • Complete blood count (CBC): This test measures the level of white blood cells; higher numbers indicate an infection. 

Sometimes healthcare providers order a throat culture to rule out strep throat, which causes symptoms similar to mono. They will swab the back of your throat to test for strep-associated bacteria. 

Stages of Mono

There are three stages of mono, which describe the progression of symptoms and their severity. Not everyone with mono will experience all three of these stages, and symptoms of mono can appear at different times throughout the infection.

The three stages of mono include:

  • Prodrome: When mono symptoms appear, usually four to six weeks after getting infected. You may start feeling more tired, “off,” or have a general sense of malaise, a smaller appetite, and a sore throat. 
  • Acute: Your symptoms may get worse during this time. This stage lasts anywhere from 2-6 weeks. 
  • Convalescent: The recovery period when symptoms gradually improve and you start to feel better. It can take several weeks to months to fully recover from mono. 


Mono treatments relieve symptoms and support the body's natural healing process while your immune system fights the virus. Common mono treatments include:

  • Rest: Your body needs rest to recover from the virus, and you may need to take time off from work or school and avoid strenuous activity while you recover. 
  • Pain relief: Over-the-counter medications, such as Tylenol (acetaminophen) and Advil (ibuprofen), can help alleviate symptoms like fever and sore throat. 
  • Hydration: Drinking fluids—especially water, tea, and soup—can help keep your body hydrated and relieve symptoms such as fatigue, headaches, and sore throat. 
  • Corticosteroids: In some cases, corticosteroid medications may be prescribed to help reduce inflammation and relieve symptoms such as swelling and inflammation of the throat. 


There is no vaccine or specific way to prevent mono, as the virus is highly contagious and spreads through close contact with an infected person. As the name "kissing disease" implies, don't kiss or have close contact with someone who has mono until they fully recover.

It is important to practice good hygiene; washing your hands frequently with soap and water, especially after contact with someone who is sick. In general, it's best to avoid sharing personal items such as drinking glasses, utensils, toothbrushes, and food.


While most people with mono will recover without complications, several potential complications can arise, including:

  • Ruptured spleen: Some people with mono will experience a swollen spleen; in some cases, it can rupture (burst) and cause severe abdominal pain. A ruptured spleen requires immediate medical attention. 
  • Liver inflammation: Mono can cause liver inflammation, leading to jaundice (yellow-colored skin), abdominal pain, and fluid buildup in the abdomen.
  • Anemia: Mono can sometimes cause a decrease in red blood cells, leading to mild anemia. Symptoms of anemia include fatigue, weakness, and shortness of breath.
  • Peritonsillar abscess: This is an infection in the throat that causes a collection of pus to travel from the tonsils in the back of the throat to the chest, causing difficulty swallowing, fever, and severe sore throat. 
  • Encephalitis: This is characterized by inflammation in the brain that can cause flu-like symptoms or confusion, dizziness, weakness, numbness, and seizures. 
  • Pleural effusion: This causes fluid build-up in the tissues surrounding the lungs, causing shortness of breath, coughing, and chest pain. 

Living With Mono

Having mono can be exhausting, and you may feel frustrated that you can’t attend work or school or engage in the sports or activities you usually enjoy. Fortunately, most people with mono recover within 2 to 6 weeks. 

The most important thing to do is rest as much as possible and avoid strenuous activities to give your body a chance to recover and heal. Adequate sleep, staying hydrated, and eating a balanced diet can help support your immune system.

Because mono can sometimes cause a swollen spleen, contact sports and lifting heavy items should be avoided for at least a month to avoid rupturing the spleen. Follow up with a healthcare provider if your symptoms are not improving or you develop new symptoms, such as jaundice, abdominal pain, trouble swallowing, or a severe headache.

Was this page helpful?
17 Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. MedlinePlus. Infectious mononucleosis.

  2. National Institutes of Health. NIH launches clinical trial of Epstein-Barr virus vaccine.

  3. Merck Manual: Consumer Version. Infectious mononucleosis.

  4. Centers for Disease Control and Prevention. About infectious mononucleosis.

  5. Lennon P, Crotty M, Fenton JE. Infectious mononucleosis. BMJ. 2015;350. doi:10.1136/bmj.h1825

  6. Pich D, Mrozek-Gorska P, Bouvet M, et al. First days in the life of naive human b lymphocytes infected with epstein-barr virus. Ambinder RF, Griffin DE, eds. mBio. 2019;10(5):e01723-19 doi:10.1128/mBio.01723-19

  7. Dunmire SK, Hogquist KA, Balfour HH. Infectious mononucleosis. Curr Top Microbiol Immunol. 2015;390(Pt 1):211-40. doi:10.1007/978-3-319-22822-8

  8. American Cancer Society. Viruses that can lead to cancer.

  9. Pourahamad M, Hooshmand F, Olyaee Nezhad S, Sepidkar A. EBV seroepidemiology in married and unmarried women and men in Iran. Rep Biochem Mol Biol. 2014;2(2):94-97.

  10. American Academy of Family Physicians. Mononucleosis.

  11. MedlinePlus. Mononucleosis (mono) tests.

  12. Centers for Disease Control and Prevention. Epstein-Barr virus and infectious mononucleosis.

  13. Balfour HH, Dunmire SK, Hogquist KA. Infectious mononucleosis. Clin Trans Immunol. 2015;4(2):e33. doi:10.1038/cti.2015.1

  14. UpToDate. Patient education: Infectious mononucleosis (mono) in adults and adolescents (beyond the basics).

  15. Herold J, Grimaldo F. Epstein-Barr virus-induced jaundice. Clin Pract Cases Emerg Med. 2020;4(1):69-71. doi:10.5811/cpcem.2019.10.45049

  16. MyHealthAlberta. Mononucleosis complications.

  17. Zhang L, Zhou P, Meng Z, et al. Infectious mononucleosis and hepatic function. Exp Ther Med. 2018;15(3):2901-2909. doi:10.3892/etm.2018.5736

Related Articles