What Is Mononucleosis?

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Infectious mononucleosis (mono) is a condition usually caused by the Epstein-Barr virus (EBV) or, less commonly, cytomegalovirus (CMV).

Mono is sometimes called "kissing disease" because it is spread through saliva and close contact.

The symptoms of a sore throat, swollen lymph glands, enlarged tonsils, and extreme fatigue are usually more pronounced in teens and young adults and can last one to two months, though someone can be considered contagious for several months. Mono is treated with rest and care for the symptoms.

Mononucleosis common symptoms

Mononucleosis Symptoms

Symptoms of mono can vary from person to person and may include some or all of the following, which may appear at different times during the course of the illness:

  • Fatigue (usually extreme)
  • Fever of 100 degrees to 103 degrees that gets worse at night
  • A sore throat
  • Swollen lymph glands in the neck and armpits
  • Swollen tonsils that may or may not have white patches on them
  • Swollen liver or spleen
  • Abdominal pain
  • A headache
  • Jaundice
  • Rash
  • Decreased appetite

When young children become infected with mononucleosis, their symptoms may be subtler and may include poor feeding and irritability. In rare cases, the tonsils may become swollen enough to require hospitalization.

Because the symptoms of mono can closely resemble strep throat—which needs to be treated with antibiotics—it is important to see a doctor. You should go to the emergency room if you cannot swallow or have a high fever that you cannot control. In very rare cases, mono can cause heart problems, so get immediate medical attention if you have chest pain, difficulty breathing, or any other cardiovascular symptoms. Contact your doctor with any other worrisome or unexplained symptoms of mono.


The Epstein-Barr virus is the primary cause of mono, but infection by cytomegalovirus (CMV) can produce a similar illness. There are also several other infectious agents that produce mono-like illnesses, including the parasite Toxoplasma gondii. Symptoms usually develop four to six weeks after you are exposed to the virus.

By age 5, about half of children have been infected by EBV, often with few or no symptoms.

About 95 percent of the adult population has been infected with EBV. Teens and young adults who haven't had the virus as a child are the ones most at risk ​of developing the symptoms of mononucleosis.

The virus is primarily spread through saliva and close contact. Besides kissing, it can spread on drinking cups and utensils. It is also spread through other bodily fluids such as mucus, blood, semen, and vaginal secretions. People remain contagious for six months after infection.

The virus never goes away but becomes dormant. It has the potential to become active again if your immune system is weakened. You may be intermittently contagious (by "shedding" the virus) and be able to spread EBV to others.


It is important to be diagnosed by a doctor because the symptoms are similar to other illnesses that have different treatment regimens. Your doctor will usually perform a thorough exam before ordering blood work or prescribing treatment. He will be looking for swollen lymph nodes in the neck and swollen tonsils, which may be covered in white or yellow patches. In severe cases, the doctor may be able to feel an enlarged liver or spleen when pushing on your belly.

Mononucleosis Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

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If the doctor suspects mono, he may order blood work which will usually reveal a higher than normal amount of white blood cells (cells that fight off infection). Mono is usually diagnosed by your symptoms or by testing your antibody levels to EBV or CMV.


Since the illness is caused by a virus, treatment is aimed at managing the symptoms. There is no cure or vaccine for mono. You should start to feel better after about 10 days, though it can take as long as three months to fully recover.

Supportive care for mono includes doing these things:

  • Get plenty of rest, at least eight hours per night.
  • Drink plenty of non-caffeinated fluids and avoid alcoholic beverages, as your liver may be inflamed.
  • To manage sore throat pain, try a warm salt water gargle or suck on a throat lozenge. Cold fluids also help to reduce discomfort and swelling.
  • Over-the-counter medications such as Tylenol (acetaminophen) and Motrin (ibuprofen) are useful in reducing a fever and treating sore throat pain. Consult your doctor or pharmacist before combining over-the-counter medications with prescription medications.
  • Prescriptions are rarely needed, but corticosteroids may be used if the tonsils are so enlarged that they block breathing and swallowing.
  • Avoid contact sports until you are fully recovered; such activities can cause an enlarged spleen to rupture.

A Word From Verywell

Getting mono can interrupt your life, including school or work obligations. It can be frustrating to feel the fatigue and pain and not have a simple pill to take that will cure it fast. You may, then, feel inspired to get back to your normal routine as your symptoms start to subside. Remember that your body is still fighting as you start to feel better. Don't push yourself. Taking care to get enough rest and maintaining good nutrition will help your body deal with the virus and get through this episode.

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Article Sources
Verywell Health 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. Centers for Disease Control and Prevention. Epstein-Barr Virus and Infectious Mononucleosis. About Infectious Mononucleosis

  2. Centers for Disease Control and Prevention. Epstein-Barr Virus and Infectious Mononucleosis. About Epstein-Barr Virus (EBV)

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