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Infectious Mononucleosis

What is infectious mononucleosis?

Infectious mononucleosis is characterized by swollen lymph glands, fever, sore throat, and extreme fatigue. It’s often spread through contact with infected saliva from the mouth. Symptoms can take between 4 to 6 weeks to appear and usually do not last beyond 4 months. Transmission is impossible to prevent because even symptom-free people can carry the virus in their saliva.

What causes infectious mononucleosis?

Infectious mononucleosis is caused by the Epstein-Barr virus (EBV). A variant of mononucleosis that is milder than EBV infectious mononucleosis is caused by the cytomegalovirus (CMV). Both EBV and CMV are members of the herpes virus family:

  • In the U.S., most adults between 35 and 40 years old have been infected with the Epstein-Barr virus. This is a very common virus. When children are infected with the virus, they usually do not experience any noticeable symptoms. However, uninfected adolescents and young adults who come in contact with the virus may develop an illness very similar to infectious mononucleosis.
  • The Epstein-Barr virus (EBV) may cause infectious mononucleosis in adolescents and young adults. However, even after the symptoms of infectious mononucleosis have disappeared, the EBV will remain dormant in the throat and blood cells during that person's lifetime. The virus can reactivate periodically, however, usually without symptoms.

What are the symptoms of infectious mononucleosis?

Mononucleosis usually lasts for 1 to 2 months. The following are the most common symptoms of mononucleosis. However, each person may experience symptoms differently. Symptoms may include:

  • Fever
  • Swollen lymph glands in the neck, armpits, and groin
  • Extreme fatigue
  • Sore throat
  • Enlarged spleen
  • Head and body aches
  • Liver involvement, such as mild liver damage that can cause temporary jaundice, a yellow discoloration of the skin and whites of the eyes due to abnormally high levels of bilirubin (bile pigmentation) in the bloodstream

Once a person has had mononucleosis, the virus remains dormant in the throat and blood cells for the rest of that person's life. Once a person has been exposed to the Epstein-Barr virus, a person is usually not at risk for developing mononucleosis again.

The symptoms of mononucleosis may resemble other medical conditions. Always talk with your healthcare provider for a diagnosis.

How is infectious mononucleosis diagnosed?

A diagnosis of mononucleosis is usually based on reported symptoms. However, diagnosis can be confirmed with specific blood tests and other lab tests, including:

  • White blood cell count, which is not diagnostic, but the presence of certain types of white blood cells (lymphocytes) may support the diagnosis
  • Heterophile antibody test or monospot test, which, if positive, indicates infectious mononucleosis

How is infectious mononucleosis treated?

Your healthcare provider will figure out the best treatment for you based on:

  • How old you are
  • Your overall health and past health
  • How sick you are
  • How well you can handle specific medicines, procedures, or therapies
  • How long the condition is expected to last
  • Your opinion and preference

Treatment for mononucleosis may include:

  • Rest (to give the body's immune system time to destroy the virus)
  • Drink plenty of liquids
  • Take over-the-counter medicine as directed for discomfort and fever
  • Corticosteroids only when necessary to reduce swelling of the throat and tonsils

What are the complications of infectious mononucleosis?

Complications of infectious mononucleosis don’t happen often. Complications may include:

  • Ruptured spleen
  • Kidney inflammation
  • Hemolytic anemia
  • Nervous system problems, such as encephalitis, meningitis, and other conditions
  • Inflammation of the heart muscle
  • Heart rhythm problems
  • Obstruction of the upper airways

Can infectious mononucleosis be prevented?

Avoid kissing or sharing dishes, food utensils, or personal items with anyone who has the infection.

When should I call my healthcare provider?

If your symptoms get worse or you have new symptoms, let your healthcare provider know.

Key points about infectious mononucleosis

  • Infectious mononucleosis is characterized by swollen lymph glands, fever, sore throat, and extreme fatigue
  • Mononucleosis usually lasts for 1 to 2 months.
  • Symptoms may include fever, swollen lymph glands in the neck, armpits, and groin, constant fatigue, sore throat, enlarged spleen, and jaundice, a yellow discoloration of the skin.
  • Treatment includes rest and plenty of liquids.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.
  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.
  • Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
  • Ask if your condition can be treated in other ways.
  • Know why a test or procedure is recommended and what the results could mean.
  • Know what to expect if you do not take the medicine or have the test or procedure.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.
Online Medical Reviewer: Lentnek, Arnold, MD
Online Medical Reviewer: Sather, Rita, RN
Date Last Reviewed: 11/1/2016
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