Infectious Mononucleosis Symptoms & Causes

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What is infectious mononucleosis?

Infectious mononucleosis, more commonly known as "mono", is a viral illness characterized by flu-like symptoms, fatigue and swollen lymph glands. It's long been nicknamed the "kissing disease" as it's easily transmitted through saliva.

Extremely contagious, mono is also difficult to prevent as many people with the virus display no symptoms. Once you or your child has had mono, the virus remains inactive in the throat and blood cells for life.

What causes infectious mononucleosis?

Mono is either caused by the Epstein-Barr virus (EBV) or the cytomegalovirus. Both are members of the herpes simplex virus family. It's often spread through contact with infected saliva (such as kissing, sneezing or sharing a glass). According to the Centers for Disease Control and Prevention, mono is difficult to prevent because even symptom-free people can carry the virus in their saliva.

Is infectious mononucleosis common?

The Epstein-Barr virus that causes mono is very common. More specifically:

  • Approximately 95 percent of adults in the United States between the ages of 35 and 40 have been exposed to the Epstein-Barr virus.
  • Uninfected adolescents and young adults who come in contact with the virus have a 50 percent chance of developing symptoms.
  • Epstein-Barr virus can reactivate periodically, however, usually without symptoms.
  • Only 20 percent of adults infected with the cytomegalovirus will develop symptoms.

What are the symptoms of infectious mononucleosis?

Mono usually lasts for one to two months. While symptoms may vary child to child, the most common include:

  • fever
  • swollen lymph glands in the neck, armpits and groin
  • constant fatigue
  • sore throat due to tonsillitis, which often makes swallowing difficult
  • enlarged spleen
  • mild liver damage that can cause temporary jaundice (a yellow discoloration of the skin and eye whites).

Once you have had mononucleosis, the virus remains inactive in the throat and blood cells for the rest of your life. The virus can reactivate, but usually without symptoms.

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