The Bowdoin Orient

April 6, 2001
Volume CXXXII, Number 20

Ask Dr. Jeff

by JEFF BENSON, M.D. DUDLEY COE HEALTH CENTER

Dear Dr. Jeff: I was recently seen in the Health Center for possible mono. I already had mono once before, and you said you weren't supposed to be able to get it again (though some people believed they had.) I tested negative this time, but you said that didn't absolutely mean I didn't have mono. I'm confused! What's the story here? L.T.

   Dear L.T.: Infectious Mononucleosis is a contagious illness characterized by fever, pharyngitis ("sore throat"), swollen lymph nodes ("glands"), and often severe fatigue. It is caused by Epstein Barr Virus, a member of the Herpesvirus family, which infects primarily the cells lining the nose and throat and B cell lymphocytes (white blood cells).
   Viral DNA is incorporated into B cell DNA, and these transformed B cells carry the infection to other organs in the body, especially the liver and spleen. Some of these infected B cells become "immortalized", forever harboring the viral genome.
   The full import of this transformation is not yet well understood, but it has been linked to a variety of disorders, including Chronic Fatigue Syndrome and certain malignancies in Africa.
   In the developing world, infection with Epstein Barr Virus is widespread and most commonly occurs in early childhood as a mild, often unnoticed "cold". In the United States, fewer than half of children have been infected by the age of 5.
   About 12 percent of susceptible college-age men and women are infected each year with the virus, and about half of them develop clinical mononucleosis. That means that nearly 1 in 50 students may come down with mono every year.
   Transmission of Epstein Barr Virus takes place through contact with infected saliva (hence mono as the "kissing disease"). The incubation period is about 30-45 days. The illness typically lasts 2-4 weeks, is almost always self-limited, and rarely requires medical intervention.
   The period of communicability, however, is prolonged, and viral shedding in saliva may persist for a year or more after the infection has "resolved".
   Because mono usually causes inflammation of the liver, and often leads to swelling of the spleen, alcohol and contact sports must be avoided during the illness.
   B cells infected with Epstein Barr Virus produce a variety of new antibodies, among them the "heterophile antibody." Most "mono tests" (for instance, the "Monospot" test we use at the Health Center) look for this heterophile antibody in a patient's serum, but test results can be difficult to interpret.
   While the antibody is present at some point during the illness in about 90% of patients, it may appear earlier or later. It usually disappears 3 or 4 months after the illness, but it may persist longer.
   In other words, a monospot test might be falsely negative if done too early, or falsely positive if done too soon after a prior (and resolved) infection-and "too early" might mean anywhere from 1 to 4 weeks, and "too soon" might mean 6 months or more!
   The heterophile antibody is not protective against Epstein Barr Virus. It is produced by infected B cells, which are prompted by the incorporated viral DNA, and it reacts with the red blood cells of other species (hence "heterophile").
   Antibodies directed against Epstein Barr Virus itself are also made soon after infection (by uninfected T cells and B cells). They are believed to confer long-term immunity. Their presence is also more straightforwardly diagnostic of an acute infection. They are detected, however, by laboratory tests which are far less common, and far more expensive.
   Another important laboratory sign of Infectious Mononucleosis is the presence of large numbers of "atypical lymphocytes" (the infected B cells). Taken alone, however, this finding is not terribly specific.
   In fact, many different viral illnesses also cause an increase in atypical lymphocytes, including those which also cause Infectious Mononucleosis-like illnesses nearly indistinguishable from Epstein Barr Virus infection (like Cytomegalovirus, Human Herpesvirus Type 6, Toxoplasmosis, and Rubella).
   In summary, then, diagnosis of mono can be a little complicated. Though it may cause short-term misery, the illness is fortunately almost always short-lived, and rarely causes complications.

Jeff Benson, M.D.
Dudley Coe Health Center

Please address any questions or comments you may have related to medical care, public health, preventive medicine, health policy, health center services, or any other issue involving health or wellness, to jbenson@bowdoin.edu - and see your answer appear here in the Features section!