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Infectious Mononucleosis
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Infections

Infectious Mononucleosis

Infectious mononucleosis, often called "the kissing disease," is a contagious viral illness most commonly caused by the Epstein-Barr virus (EBV).

What is infectious mononucleosis (mono)?

Infectious mononucleosis (mono) is a disease caused by viruses. The most common cause is the Epstein-Barr virus (EBV). Mono is contagious, which means it can spread from person to person. It is common among teenagers and young adults, especially college students.

What causes infectious mononucleosis (mono)?

Mono can be caused by many different viruses, but it is most often caused by the Epstein-Barr virus (EBV). EBV is found all over the world. Most people get an EBV infection at some point in their lives, but only some will develop the symptoms of mono. EBV infections often happen during childhood or when someone is a young adult. EBV infections in children usually do not cause symptoms, or they are difficult to distinguish from other common childhood illnesses like the flu. Teens and young adults who get EBV are more likely to have symptoms that are typical of mono.

EBV and the other viruses that cause mono are usually spread through body fluids, especially saliva. This means that you can get it through kissing, which is why mono is sometimes called "the kissing disease." You can also get these viruses if you share food, drinks, forks, spoons, or lip balm with someone who has mono. Other less common ways of getting an infection are through blood transfusions, organ transplants, and blood and semen during sexual contact.

What are the symptoms of infectious mononucleosis (mono)?

The symptoms of mono usually start four to six weeks after you get the infection, though they may start sooner in young children. Symptoms often develop slowly and may not all happen at the same time. They can include:

  • Extreme fatigue
  • Fever
  • Sore throat
  • Head and body aches
  • Swollen lymph glands in your neck and armpits
  • Rash
  • Swollen liver, spleen, or both (these are less common symptoms)

Most people get better in two to four weeks. However, some people may feel fatigued for several more weeks. Occasionally, the symptoms can last for six months or longer.

How is infectious mononucleosis (mono) diagnosed?

Your healthcare provider may diagnose mono based on your symptoms and a physical exam. The exam will include checking to see if your lymph nodes, tonsils, liver, or spleen are swollen. In some cases, your provider might also order a mono test to confirm the diagnosis.

What are the treatments for infectious mononucleosis (mono)?

  • Drinking plenty of fluids to avoid dehydration.
  • Getting lots of rest.
  • Taking over-the-counter medications for pain and fever. Do not give aspirin to children or teens because it may cause Reye syndrome, a rare, serious illness that can affect the brain and liver.

If you have severe symptoms, your provider may suggest additional treatment based on which organs in your body are affected by the mono.

Antibiotics do not treat viral infections and therefore do not help with mono. If you develop a bacterial infection such as strep throat alongside mono, you may need antibiotics; however, you should not take penicillin antibiotics like ampicillin or amoxicillin, as they can cause a rash in people who have mono.

Mono can cause an enlarged spleen, which could rupture and cause a medical emergency. To protect the spleen, providers recommend avoiding intense exercise and contact sports until you fully recover, which takes about a month.

Can infectious mononucleosis (mono) be prevented?

There is no vaccine to protect against mono. To lower your chance of getting or spreading mono:

  • Don't share food, drinks, forks, spoons, or lip balm with anyone, especially if you or the other person has mono.
  • Don't kiss someone if you or the other person has mono.
  • Wash your hands often with soap and water.

Frequently Asked Questions

fter catching Epstein‑Barr virus, symptoms typically start 4–6 weeks later. Early signs include a sudden sore throat, swollen tonsils, fatigue, low‑grade fever, and swollen lymph nodes in the neck or armpits. If you notice these, consider a doctor’s visit for a monospot test or EBV antibody panel. Can I still attend school or work while I have infectious mononucleosis, and how long should I stay home to avoid spreading it?::Mono spreads through saliva, so avoid kissing, sharing drinks, or utensils. Most people are contagious for 2–3 weeks after symptoms begin. If you feel well enough to work or study, limit close contact with others, especially in crowded settings. If you have a fever, severe sore throat, or fatigue, it’s best to stay home until symptoms improve. What are the best ways to manage the severe sore throat and fatigue associated with mono?::Use over‑the‑counter pain relievers such as acetaminophen or ibuprofen for pain and fever. Stay hydrated, sip warm teas, and consider throat lozenges or saltwater gargles. Rest is crucial; aim for 7–9 hours of sleep each night and avoid strenuous activity until energy levels return. Are there any complications that can arise from mono, such as splenic rupture, and how can I reduce the risk?::Yes, mono can cause splenomegaly (enlarged spleen) and increase the risk of splenic rupture, especially during contact sports or heavy lifting. Get a physical exam to check spleen size; if enlarged, avoid contact sports, heavy lifting, and strenuous exercise for at least 4–6 weeks. If you notice sudden sharp pain in the left upper abdomen, seek emergency care immediately.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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