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Quick Facts

Infectious Mononucleosis (Mono)


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Last full review/revision Mar 2020| Content last modified Mar 2020
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What is infectious mononucleosis?

Infectious mononucleosis, often called mono, is a viral infection that is most common in teens and young adults.

  • Mono is spread by close contact, such as kissing, with infected people

  • Symptoms include a very sore throat, extreme tiredness, and swollen lymph nodes in your neck

  • People with mono usually feel better after about 2 weeks, but some people may feel very tired for weeks or even months

  • Acetaminophen or ibuprofen lowers fever and lessens pain

What causes mono?

Mono is caused by the Epstein-Barr virus, a type of herpesvirus. Infection with Epstein-Barr virus (EBV) is common, but not everyone who gets it gets mono. Many people with EBV infection have no symptoms or very mild symptoms.

What are the symptoms of mono?

Symptoms of mono include:

  • Extreme tiredness—this is usually most severe during the first 2 to 3 weeks

  • Fever, up to about 103° F (39.4° C)

  • Very sore throat—there may be pus at the back of your throat

  • Swollen lymph nodes, especially in your neck (lymph nodes are tiny, bean-shaped parts of your immune system that help fight off infections)

You can have mono without having all of these symptoms.

About half of people with mono have a swollen spleen. Your spleen is an organ in the left side of your belly just below your ribcage. It's about the size of a fist. The spleen makes blood cells that help your immune system and also gets rid of blood cells that are old or abnormal. A spleen is more likely to burst if your belly is injured while your spleen is swollen.

If mono is very severe, it can cause low blood count and problems with your liver, heart, and nerves.

How can doctors tell if I have mono?

Doctors may suspect mono from your symptoms, especially if you have swollen lymph nodes in your neck. To know for sure, they'll do blood tests.

How do doctors treat mono?

There are no medicines to cure mono. Antiviral drugs don't help. Doctors will:

  • Tell you to rest for a week or two, when you’re feeling the most tired and weak

  • Have you take acetaminophen or ibuprofen to help your fever and pain

  • Have you take corticosteroids, if your tonsils are so swollen and painful that you're having trouble swallowing or breathing

After 2 weeks, as you start to feel better, you can be more active—just don’t lift anything heavy or play contact sports (like football) until your doctor tells you that your spleen is back to its normal size.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
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