What Are the Symptoms of Mono?

Swollen Glands
Mono Swollen Glands. Science Photo Library / Getty Images

What is Mono?

Mono, short for infectious mononucleosis, is a condition usually caused by the Epstein-Barr virus (EBV) and, less commonly, cytomegalovirus (CMV). Mono is sometimes called "kissing disease" because it is spread through saliva and close contact. Symptoms usually develop 4-6 weeks after you are exposed to the virus.

People are commonly infected with EBV, but it doesn't always lead to symptoms, especially when people become infected as children.

In fact, it only causes mono 35-50% of the time, and these cases are usually in teenagers and young adults (one in four teens who are exposed to the virus will develop infectious mononucleosis). For this reason, age is an important factor in diagnosing mono.

Symptoms of Mono

Mono may include some or all of the following symptoms which may appear at different times during the course of the illness:

  • fatigue (usually extreme)
  • fever of 100-103F (gets worse at night)
  • sore throat
  • swollen lymph glands
  • swollen tonsils that may or may not have white patches on them
  • swollen liver or spleen (rare)
  • abdominal pain
  • headache
  • jaundice
  • rash
  • decreased appetite

The severity of symptoms varies greatly between individuals. When young children become infected with mononucleosis, (which is rare), their symptoms may be more subtle and may include poor feeding and irritability. In rare cases symptoms may become severe 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.

How is Mono Diagnosed?

Mono is diagnosed using a monospot test, or by testing your antibody levels to EBV or CMV. The symptoms of mono can last quite a while, with an average being 1-2 months. Since the illness is caused by a virus, treatment is aimed at managing the symptoms.

There is no cure for mono. The virus never goes away but becomes dormant. It may become active again, but people rarely experience "mono" twice. Some people can develop chronic fatigue from the Epstein-Barr Virus. Your doctor may suspect chronic fatigue syndrome if your symptoms of mono go on longer than 4 months.


CDC. Epstein-Barr Virus and Infectious Mononucleosis. Accessed: January 9, 2017 from https://www.cdc.gov/epstein-barr/about-mono.html

emedicinehealth. Mononucleosis. Accessed: January 9, 2017 from http://www.emedicinehealth.com/mononucleosis/page2_em.htm

University Health Service University of Michigan. Infectious Mononucleosis. Accessed: January 9, 2017 from https://www.uhs.umich.edu/mono

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