Signs and symptoms of mononucleosis may include:

• Fatigue
• Weakness
• Sore throat, perhaps a strep throat that doesn't get better with antibiotics
• Fever
• Swollen lymph nodes in your neck and armpits
• Swollen tonsils
• Headache
• Skin rash
• Loss of appetite
• Soft, swollen spleen
• Night sweats

The virus typically has an incubation period of four to eight weeks, although in young children this period is shorter. Signs and symptoms such as fever and sore throat usually lessen within a couple of weeks, although fatigue, enlarged lymph nodes and a swollen spleen may last for a few weeks longer.

When to see your doctor
If you've been experiencing the above symptoms, you may have mononucleosis.

If rest and a healthy diet don't ease your symptoms within a week or two or if your symptoms recur, see your doctor.

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The cause of mononucleosis is the Epstein-Barr virus, although similar signs and symptoms are sometimes caused by cytomegalovirus.

Mononucleosis usually isn't very serious. Most adults have been exposed to the Epstein-Barr virus and have built up antibodies. They're immune and won't get mononucleosis again.

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Enlargement of the spleen
Among significant complications of mononucleosis is enlargement of the spleen. In extreme cases, your spleen may rupture, causing sharp, sudden pain in the left side of your upper abdomen. If such pain occurs, seek medical attention immediately — you may need surgery.

Liver issues
Problems with your liver also may occur:

• Hepatitis. You may experience mild liver inflammation (hepatitis).
• Jaundice. A yellowing of your skin and the whites of your eyes (jaundice) also occurs occasionally, usually in people older than 35.

Less common complications
Mononucleosis can also result in the following less common complications:

• Anemia — a decrease in red blood cells and in hemoglobin, an iron-rich protein in red blood cells
• Thrombocytopenia — low count of platelets, which are blood cells involved in clotting
• Inflammation of the heart
• Complications involving the nervous system (meningitis, encephalitis, Guillain-Barre syndrome)
• Swollen tonsils, leading to obstructed breathing

The Epstein-Barr virus can cause much more serious illness in people who have impaired immune systems, such as people with HIV/AIDS or people taking drugs to suppress immunity after an organ transplant.

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If you suspect you have mononucleosis, you're likely to start by first seeing your family doctor. Because appointments can be brief, and because there's often a lot of ground to cover, it's a good idea to be well prepared for your appointment. Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including any major stresses, recent life changes or exposure to anyone with mononucleosis.
• Bring a list of all medications, as well as any vitamins or supplements, that you're taking.
• Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions ahead of time will help you make the most of your time together. List your questions from most important to least important in case time runs out. For mononucleosis, some basic questions to ask your doctor include:

• What is likely causing my symptoms or condition?
• Other than the most likely cause, what are other possible causes for my symptoms or condition?
• What kinds of tests do I need?
• I have these other health conditions. How can I best manage them?
• Are there any restrictions that I need to follow?
• Do I need to stay home from work or school and for how long?
• When can I return to strenuous activities and contact sports?
• Are there any medications I need to avoid with mononucleosis?
• Are there any brochures or other printed material that I can take home with me? What Web sites do you recommend?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over points you want to spend more time on. Your doctor may ask:

• When did you first begin experiencing symptoms?
• Have you been exposed to anyone with mononucleosis?
• Have your symptoms been continuous, or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?

What you can do in the meantime
If you think you have mononucleosis and are waiting for your appointment, get adequate rest and drink fluids. These are the primary treatments for mono. To avoid spreading the infection, don't kiss anyone or share items such as glasses, utensils, foods or drinks. Avoid strenuous activity and contact sports.

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Physical exam
Your doctor may suspect mononucleosis based on your signs and symptoms and a physical examination. He or she will be looking for signs like swollen lymph nodes, tonsils, liver or spleen, as well as evaluate you based on the symptoms you describe.

Blood tests

• Antibody tests. If there's a need for additional confirmation, a monospot test may be done to check your blood for antibodies to the Epstein-Barr virus. This screening test gives results within a day. But it may not detect the infection during the first week of the illness. A different antibody blood test requires a longer result time, but can detect the disease even within the first week of symptoms.
• White blood cell count. Your doctor may use other blood tests to look for an elevated number of white blood cells (lymphocytes) or abnormal-looking lymphocytes. These blood tests won't confirm mononucleosis, but they may suggest it as a possibility.

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There's no specific therapy available to treat infectious mononucleosis. Antibiotics don't work against viral infections such as mono. Treatment mainly involves bed rest and adequate fluid intake.

Medications

• Treating secondary infections. Occasionally, a streptococcal (strep) infection accompanies the sore throat of mononucleosis. You may also develop a sinus infection or an infection of your tonsils (tonsillitis). If so, you may need treatment with antibiotics for these accompanying bacterial infections.
• Risk of rash with some medications. Some people with mononucleosis who take ampicillin (Principen), amoxicillin (Amoxil, Trimox), or amoxicillin and clavulanate (Augmentin) may develop a rash, but this doesn't mean that they're allergic to the antibiotic. If needed, other antibiotics that are less likely to cause a rash are available to treat infections that may accompany mononucleosis.
• Corticosteroids. To ease some of your symptoms, such as severe swelling of your throat and tonsils, your doctor may prescribe a corticosteroid medication such as prednisone.

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In addition to getting plenty of bed rest, these steps can help relieve symptoms of mononucleosis:

• Drink plenty of water and fruit juices. Fluids help relieve fever and sore throat and prevent dehydration.
• Take an over-the-counter pain reliever. Use pain relievers such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin, others) as needed. These medicines have no antiviral properties. The only reasons to take them are to relieve pain or a fever. Don't give aspirin to a child under age 16. Aspirin may trigger a rare but potentially fatal disorder known as Reye's syndrome.
• Gargle with salt water. Do this several times a day to relieve sore throat. Mix 1/2 teaspoon (2.5 grams) salt in 8 ounces (237 milliliters) of warm water.

Wait to return to sports and some other activities
Most signs and symptoms of mononucleosis ease within a few weeks, but it may be two to three months before you feel completely normal. The more rest you get, the sooner you should recover.

Returning to your usual schedule too soon can increase the risk of a relapse. If you're an athlete, be cautious about returning to strenuous activities or contact sports, especially if your spleen is enlarged, because of the increased risk of rupturing the spleen.

Children with mononucleosis and an enlarged spleen shouldn't engage in vigorous activities, roughhousing or contact sports for the same reason. Rupture of the spleen results in severe bleeding and is a medical emergency. Doctors suggest you avoid contact sports for at least one month after you've had mononucleosis, depending on how long it takes your spleen to return to normal size.

Although you may not be able to return to vigorous activities right away, your doctor may recommend gradual exercise to help you rebuild your strength as you recover from mononucleosis.

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Mononucleosis can be a prolonged condition, keeping you at home for weeks as you recover. But be patient with your body as it fights the infection.

For young people, having mononucleosis will mean some missed activities — classes, team practices and parties. Without doubt, you'll need to take it easy for a while.

If you have mononucleosis, you don't necessarily need to be quarantined. Many people are already immune to the Epstein-Barr virus that causes the disease because of prior exposure to the virus as a child. But plan on staying home from school and other activities until you're feeling better.

Seek the help of friends and family as you recover from mononucleosis. College students should also contact the campus student health center staff for assistance or treatment, if necessary.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Mononucleosis is spread through saliva. If you're infected, you can help prevent spreading the virus to others by not kissing them and by not sharing food, dishes, glasses and utensils until several days after your fever has subsided and even longer, if possible.

The Epstein-Barr virus may persist in your saliva for months after the infection. There's no vaccine to prevent mononucleosis.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.