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What Is Mononucleosis?

Mononucleosis (mono) is a group of symptoms usually caused by a virus. In teens it can cause flu-like symptoms such as:

  • a fever
  • muscle aches
  • tiredness
  • a sore throat

These go away on their own after a few weeks of rest and plenty of fluids.

What Causes Mononucleosis?

Infectious mononucleosis (pronounced: mah-no-noo-klee-OH-sus), often called "mono" or "the kissing disease," is an infection usually caused by the Epstein-Barr virus (EBV). EBV is very common, and many people are exposed to the virus at some time in childhood.

Not everyone who is exposed to EBV develops mono, though. As with many viruses, it is possible to be exposed to and infected with EBV without becoming sick.

People who have been infected with EBV will carry the virus for the rest of their lives — even if they never have any signs or symptoms of mono. People who do show symptoms of having mono probably will not get sick or have symptoms again.

Although EBV is the most common cause of mono, other viruses, such as cytomegalovirus (pronounced: sye-toe-meh-guh-low-VYE-rus), can cause a similar illness. Like EBV, cytomegalovirus stays in the body for life and may not cause any symptoms.

How Do People Get Mono?

One common way to "catch" mono is by kissing someone who has been infected, which is how the illness got nicknamed the "kissing disease." If you've never been infected with EBV, kissing someone who is infected can put you at risk for getting the disease.

But what if you haven't kissed anyone? You can also get mononucleosis through other types of contact with saliva (spit), such as by sharing a drink, a toothbrush, an eating utensil, or even lip gloss, lipstick, or lip balm with someone who is infected with EBV. Researchers believe that mono may be passed sexually as well.

Experts think people with mono are most contagious from the time they first get infected and then for the first 18 months after getting mono. But, because EBV stays in the body for life, the virus can show up in a person's saliva from time to time, and there's a chance that person may be contagious during these times, even if he or she feels OK.

Some people who have the virus in their bodies never have any symptoms, but it is still possible for them to pass it to others.

What Are the Signs & Symptoms of Mononucleosis?

Symptoms usually begin to appear about 4 to 7 weeks after infection with the virus. Signs that you may have mono include:

  • being very tired
  • a fever
  • sore throat with swollen tonsils that may have white patches
  • loss of appetite
  • swollen lymph nodes (or glands) in your neck, underarms, and groin
  • headaches
  • sore muscles
  • weakness
  • larger-than-normal liver or spleen
  • skin rash
  • belly pain

People who have mono may have different combinations of these symptoms, and some may have symptoms so mild that they hardly notice them. Some people who get infected with EBV might not have any symptoms.

How Is Mono Diagnosed?

See a doctor if you have a fever, sore throat, and swollen glands, or if you are unusually tired for no clear reason. The symptoms of mono also can be signs of other illnesses, like the flu or strep throat.

To diagnose mono, the doctor may do a blood test and an exam to check for things like swollen tonsils and an enlarged liver or spleen, which often is a sign of the infection.

How Is Mono Treated?

There is no cure for mononucleosis. Mono needs to run its course naturally. So the best treatment for mono is plenty of rest, especially early in the illness when symptoms are the most severe.

Symptoms may last 2 to 4 weeks, and some people feel tired for several weeks longer. That's why it's important to take care of yourself and get lots of rest.

For fever and aching muscles, try taking acetaminophen or ibuprofen. Don't take aspirin unless your doctor tells you to: Aspirin has been linked to a serious disease in kids and teens called Reye syndrome, which can lead to liver failure and death.

Because mono is caused by a virus, antibiotics such as penicillin won't help unless you have an additional infection like strep throat. In fact, some antibiotics can even cause a rash if you take them while you have mono.

Although there's no magic pill for mono, you can do some things to feel better. The best treatment is to get plenty of rest, especially during the beginning stages of the illness when your symptoms are the worst. Stay home from school, sports, and other activities and rest up in bed.

When you start feeling better, take it slow and don't overdo it. Although you can return to school once your fever disappears, you may still feel tired. Your body will tell you when it's time to rest — listen to it. By taking good care of yourself and resting as much as you need to, you will soon be back to normal, usually within a few weeks.

What Else Should I Know?

Doctors recommend avoiding sports and activity for at least a month after someone has mono. That's because the spleen is often enlarged temporarily and can burst easily, causing internal bleeding and belly pain. If this happens, you'll need emergency surgery. Skip vigorous activities, contact sports, cheerleading, weightlifting, or even wrestling with your little siblings or your friends until your doctor gives you the OK.

As you recover, make sure you don't share the virus with your friends and family. Wash your hands often, sneeze or cough into a tissue or your elbow (not your hands), and keep your drinks and eating utensils to yourself. This is one time when your friends and family will thank you for being selfish.

Reviewed by: Elana Pearl Ben-Joseph, MD
Date Reviewed: 01-10-2016

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