Please note: This information was current at the time of publication but now may be out of date. This handout provides a general overview and may not apply to everyone. 

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Am Fam Physician. 2004;70(7):1289-1290

What is infectious mononucleosis?

Infectious mononucleosis (say: in-feck-shuss mon-oh-new-clee-oh-siss), or mono, often is caused by the Epstein-Barr virus. Mono usually is not serious, but some people with mono feel very tired and have pain in their joints that lasts for several weeks.

Who gets mono and why?

Mono is most common in older children, teenagers, and young adults. The virus is spread by contact with the saliva of someone who had the infection within the past few months. Mono can be spread by kissing a person who is infected or by sharing a glass, bottle, or eating utensils.

Most people get mono by the time they are adults. But most people have a very mild infection that might be mistaken for the flu.

How can my doctor tell I have mono?

People with mono usually have a sore throat, fever, swollen glands, and pus on their tonsils. Their liver and spleen might be tender and larger than normal. Your doctor might want you to have blood tests. He or she might want to test you for other sicknesses that are like mono.

How is mono treated?

The most important thing you can do when you have mono is get plenty of rest and drink enough liquids. You may want to take a pain reliever such as acetaminophen (one brand name: Tylenol) or ibuprofen (some brand names: Advil, Motrin, Nuprin). Do not give aspirin to children with mono. If your throat is very sore or if your tonsils are swollen, your doctor might prescribe medicines called corticosteroids.

Because mono is caused by a virus, antibiotics would not help you get better. But some people with mono get strep throat at the same time. Antibiotics will help strep throat go away.

What can I expect?

Most people with mono feel better after one month. Some people feel tired and sleep more than normal for as long as six months.

If you have a job, it is a good idea to let your human resources department know that you are sick with mono. If you are not able to work for a long time, you might be able to take a medical leave of absence.

If you are a student, talk to your guidance counselor. He or she will help you decide what to do if you will be out of school for a long time.

Is mono ever dangerous?

Sometimes mono can cause serious problems. One problem is with the spleen. The spleen is an organ in the upper part of your abdomen on the left side. In people with mono, sometimes the spleen grows very large and tears open. This is called a rupture. This happens to only about one in 1,000 people with mono. About one half of these ruptures happen during contact sports, such as football. If you get mono, you should not play sports for at least four weeks. Your doctor might want you to have an ultrasound test before you go back to sports.

Mono also can affect your liver. If you have mono, you should not drink alcohol while you are sick. If you notice a yellow color to your skin or if you begin to bruise easily, see your doctor.

How can I prevent mono?

The best way to keep from getting mono is to avoid contact with the saliva of infected people. Do not share bottles, cans, glasses, plates, or eating utensils. Do not kiss a person who had mono recently.

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