Mononucleosis: the kissing disease

Mononucleosis the kissing disease

Mononucleosis. We know that it’s often called the “kissing disease,” and that people who have it sleep a lot. But what actually causes this exhausting illness?

Infectious mononucleosis, or “mono,” as it is commonly known, is caused by a virus. It is so named, because the disease causes your white blood cells—the mononuclear cells—to increase greatly. A number of viruses can cause mono, but the most common is the herpes-type virus known as the Epstein-Barr virus (EBV).

Many people contract mononucleosis as children but remain asymptomatic. If you contract it in your teens or 20s, it generally does become symptomatic. Adults over 35 are generally less likely to contract mononucleosis, but those who do often become quite ill.

Mononucleosis is quite contagious, and is usually transmitted from person to person through the exchange of saliva. Transmission can occur through the air—via coughing or sneezing—or by sharing contaminated toothbrushes or eating and drinking utensils. However, mono is most often transmitted through kissing—especially intimate kissing—thus accounting for its street name.

Symptoms and diagnosis

Because the symptoms of mononucleosis often mirror those of a number of other conditions, it can be hard to diagnose. Symptoms usually include:

  • Fever
  • Sore throat
  • Enlarged lymph nodes (swollen glands)
  • Exhaustion

Less often, symptoms can include nausea, vomiting, loss of appetite, rash, or jaundice. And in extremely rare cases, some patients report an “Alice in Wonderland” effect, whereby their eyesight is affected such that the size of objects appear distorted.

Generally these symptoms will appear between four and six weeks after exposure to the virus, and usually last from two to four weeks. In some cases, however, symptoms—especially the debilitating exhaustion—can last up to several months. To diagnose mono, physicians will first question you about your symptoms and conduct a thorough examination. If mono is suspected, a blood test known as a “mono-spot” is done to look for certain antibodies that are usually (but not always) present during a bout with mononucleosis. Other, more sophisticated antibody tests are also available if necessary.


There is no vaccine to prevent you from contracting mononucleosis. However, once you’ve had it, you automatically develop a resistance to the virus. This makes subsequent bouts of mono next to impossible. In fact, most of us are exposed to and infected by the Epstein-Barr virus sometime in our lives. However, most of us never develop mononucleosis or any of the other possible (but very rare) complications from EBV, which can include pneumonia, anemia and/or central nervous system complications.

“Despite what has been previously believed, mononucleosis is not the cause of chronic fatigue syndrome,” notes Dr. Richard Parker, associate medical director for general internal medicine at Boston’s Beth Israel Deaconess Medical Center.

Since mono is very contagious, you should avoid undo contact (where saliva can be exchanged) with a person who has mono while the disease is active. Complete isolation of mono patients, however, is not necessary.

Treatment: no magic pill

As with prevention, there is no treatment for mononucleosis. However, like other virus-based diseases (such as the common cold) mono will usually run its course and cure itself. Until it does, therapy is generally confined to treating the symptoms, including bedrest, drinking plenty of fluids, using cough drops, and gargling with warm, salty water. Aspirin, acetaminophen-based products (such as Tylenol) or ibuprofen-based products (such as Advil) will help control fever. But under no circumstances should aspirin be given to children, due to the risk of Reye’s syndrome, a very serious and sometimes fatal condition.

In addition, mono patients should avoid taking antibiotics. Why? Antibiotics do not cure mononucleosis, but antibiotics (especially ampicillin) can cause or exacerbate a severe rash in patients with mono. However, as Dr. Parker points out, certain antibiotics are prescribed for patients with mono who have contracted a secondary bacterial infection, such as strep throat.

Complications are rare but serious

As noted, mono generally runs its course until you eventually feel better. In extremely rare instances, however, serious complications from mononucleosis can evolve. The most serious is enlargement and rupture of the spleen—a fist-sized organ located on the upper left side of the abdomen that serves as both a blood reservoir and, along with the liver, controls the red blood cells in the body. Enlargement and rupture result because the viral infection that causes mono forces the spleen to handle far more blood cells than normal.

Though rare in mono patients, rupture of the spleen is serious and can prove fatal if not treated quickly. Accordingly, mono patients should be alert to the following symptoms of an enlarged or ruptured spleen and seek medical treatment immediately if they suffer from any of them.

  • Pain in the upper left side of the abdomen
  • Lightheadedness
  • Trouble breathing
  • The feeling that your heart is beating very fast and very hard
  • Bleeding more easily than normal

Recuperation can be very long

Mononucleosis will generally run its course within two to four weeks, although the feeling of tiredness can linger much longer (three to four months). Patients are advised to return to normal activities slowly as they begin to regain their full strength. There is, however, one major caveat. Any mono patient who has shown evidence of enlargement of the spleen should avoid strenuous activity—including contact sports—until cleared by a physician to return to such activity.

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