What is mononucleosis?

Mononucleosis, also known as “mono,” is an infectious disease that is usually caused by the Epstein-Barr virus (a herpes virus). Other viruses can also cause mononucleosis. Mononucleosis is not considered a serious illness, but its symptoms may be severe enough to prevent a person from engaging in normal activities for several weeks. The classic symptoms of this illness tend to occur more frequently among teenagers, especially those 15 to 17 years old, and in adults in their 20s.

What are the symptoms of mononucleosis?

The most common symptoms of mononucleosis are fever, sore throat, and swollen lymph glands in the neck, under the arms, and in the groin area. Other symptoms include the following:

  • Fatigue
  • Muscle aches or weakness
  • White patches in the throat
  • Skin rash
  • Headache
  • Loss of appetite

In addition to these symptoms, the spleen (an abdominal organ that stores and filters blood) may become enlarged. About half of those who have mononucleosis have enlargement of the spleen sometime during the course of their illness.

The incubation period - the time it takes symptoms to appear after a person becomes infected with the virus - can be 4 to 6 weeks. Symptoms of mononucleosis usually last for 1 to 4 weeks, but it might take as long as 2 months before you feel well enough to resume all of your normal activities.

How is mononucleosis spread?

Mononucleosis is usually acquired by contact with the saliva or mucus of a person who is infected with or is carrying the virus. (Mononucleosis is also known as the “kissing disease,” because it can be acquired through kissing.) Occasionally, it can be spread by coughing or sneezing, or when an infected person shares food or tableware with another person.

It is nearly impossible to prevent Epstein-Barr infections because most healthy people carry the virus and can pass it on to others. After the virus enters the body, the immune system begins to produce antibodies against it. The Epstein-Barr virus remains inactive in the body throughout life, but it may become active from time to time. However, reactivation of the virus does not result in clinical symptoms in individuals who have normal immune systems.

How common is mononucleosis?

The Epstein-Barr virus is a very common virus. A large number of adults develop antibodies to the Epstein-Barr virus by the time they are 40 years old, which means that they have been infected with the virus at some point in their lives. Most individuals are infected with this virus early in life (before the adolescent years), and most of these children have no or very mild symptoms from it. Adolescents, especially teens 15 to 17 years of age, and young adults who become infected with this virus are most likely to develop the classic symptoms of mononucleosis.

How is mononucleosis diagnosed?

Mononucleosis is usually diagnosed based on the patient’s symptoms of fever, sore throat, and swollen lymph glands. The doctor may order blood tests, particularly the mono spot test. This test detects antibodies to the Epstein-Barr virus, but sometimes it is inaccurate (yields a false negative) during the first week of infection. Other blood tests, such as a complete blood count, might be done to see if the number of lymphocytes is higher than normal, which may support the diagnosis. Occasionally, titers of antibodies against the viruses that cause mononucleosis may need to be done to confirm the diagnosis.

How is mononucleosis treated?

There are no medications that can treat mononucleosis because antibiotics and antiviral drugs are not effective against the virus. If you are diagnosed with mononucleosis, here are some suggestions for how to deal with it:

  • Get lots of rest, preferably bed rest, especially the first week or two.
  • Drink plenty of water and other fluids.
  • Take nonprescription pain relievers, such as ibuprofen (or acetaminophen, if you cannot take ibuprofen) to help relieve the
    fever and muscle aches that are common symptoms.
  • To help soothe a painful sore throat, use throat lozenges, drink cold beverages or eat frozen desserts, such as popsicles.
  • Gargle with salt water several times a day if your throat feels sore. Prepare the salt water solution by dissolving about one-half teaspoon of salt in one cup (8 ounces) of warm water.
  • Avoid any strenuous physical activity, such as exercise, heavy lifting, or contact sports, for at least 4 to 6 weeks after being
    diagnosed with mononucleosis. This is to prevent rupture of the spleen, which is fragile during mononucleosis.

Are there any symptoms that require medical attention?

If you have an unusually painful or a persistent sore throat or have difficulty breathing or swallowing because your tonsils are swollen, see a healthcare professional. Your doctor may perform a throat culture to see if you have a streptococcus infection (strep throat), which is not uncommon when you have mononucleosis, and which can be treated with antibiotics. You can also develop airway difficulties from enlarged tonsils.

If you have mononucleosis and feel a sudden, sharp, severe pain in your left side in the upper abdomen, go to a hospital or call 999. The pain may be a sign of a ruptured spleen, which is a very rare complication of mononucleosis. Symptoms lasting longer than 4 to 6 weeks are very rarely due to the effects of mononucleosis.

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