Of all the infections that afflict the nose and throat, few cause as much reaction and worry as mono.  Just the word carries a lot more weight than the phrase viral illness, and certainly more than the word cold.

But is mono always a serious illness?  How is it different than other infections of the nose and throat, such as strep and colds?

It turns out that many, many people can have the illness mono and not be very ill at all.  So how do you know when mono is a problem, and what sort of problems can it cause?

Mono is shorthand for an infection called infectious mononucleosis.  It turns out that if you look at white cells, some have one nucleus in the center of their cells, and others have many.   The ones with one nucleus can be referred to as monocytes, and in mono, there tend to be lots of them.  Hence the term infectious mononucleosis- or an infection that causes there to be many white cells with one nucleus each circulating.

There are two germs that can cause mono, but the vast majority are caused by one.  The infrequent cause is a virus called CMV which we will not discuss much further.  The main cause of mono is a virus called the Epstein-Barr Virus, or EBV, because Dr. Epstein and Dr. Barr first described it.  The EBV is one of 8 types of herpes viruses, and is also referred to as herpes virus 4.  Other herpes viruses are very well known, including the ones that cause cold sores (herpes virus 1 and 2), chickenpox and shingles (herpes virus 3), the CMV we mentioned above (herpes virus 5), and roseola (herpes virus 6).

Although many familiar illnesses are in the Herpes family, EBV stands out as causing a particular illness, mono.  Like all the illnesses in the herpes family, once you have had the illness, you tend not to be able to catch it again.  There are no recurring features of mono like those seen in some other herpes virus infections.

But, the EBV germ, once it causes mono, hangs around for a very long time.  It can take a year to no longer be contagious!

The EBV germ infects three main parts of the body:

1.  The throat

2.  The white blood cells

3.  Certain parts of many cells called mitochondria
4.  The Spleen

For nearly everyone with mono, it is the infection in the throat that is how everyone experiences mono.

For the vast majority of people mono is a very bad sore throat, and swollen glands.

Many people find the sore throat of mono hurts quite intensely, and is more painful than most other viral sore throats, and even strep.

The swollen glands can be tremendously large.  If some of the swollen glands are the tonsils, their enlargement can get in the way of breathing.

The EBV that causes mono attaches itself quite well to a particular type of white blood cell, the cell that makes all the various antibodies, the B-cell.   In infecting the B-cell, EBV provokes the immune system.  This is what leads to such large swollen glands in the neck noted above.   With the B-cells infected, the amount of  various antibodies circulating in the blood goes way up, an event that usually passes without any symptoms.  But one set of antibodies that is produced in mono leaves about 90% of people with it sensitive to amoxicillin during their infection.  The antibodies to amoxicillin do not create an allergy, but if you take amoxicillin while infected with mono, you are likely to get a rash with a lot of small red bumps.

The Mitochondria
Mitochondria are the part of nearly every cell that makes the energy for the cell.  This is where fuel we eat primarily gets burned, releasing its energy, which the mitochondria turn into a storable reservoir of energy.
No mitochondria, no energy, no work done.  It turns out the EBV, and so mono, attacks mitochondria.  This is more likely the older you are when you get mono.  So kids who have not yet entered puberty rarely experience the lethargy mono brings to adolescents.  Sometimes the mono can be so debilitating to the mitochondria that the affected person has little energy to even get out of bed.  In adolescents a profound lethargy can often last 1-2 months.  Rarely, it appears to be able to persist for years and cause chronic fatigue.

The Spleen
The spleen is an important organ of the immune system that lies just under the left lower edge of the ribs.  It filters blood, and is a rich area of white blood cell activity.  In mono, the spleen often is enlarged, usually not too badly.  But sometimes it gets very tight, like a tight water balloon, and very rarely, the enlarged spleen can pop like a balloon.  This is a very rare event, but is the reason people with mono might be told to avoid hitting that area of the body for 6 weeks from the start of the illness.

BOTTOM LINE
1.  When it comes to sore throats, there are basically two types of infections:  viral and strep.  Strep is a bacteria, and the only type of bacteria that causes  sore throats commonly in children.

2.  If you have a sore throat and get tested for strep and find you do not have strep, you almost certainly are infected with a virus

3.  Mono then, is one of a large number of possible viral infections of the throat.

4.  As with all viral infections of the throat, antibiotics do not help at all.  In fact, almost no drugs help beyond the pain relief of ibuprofen.

5.  In one situation, medication might be helpful for mono.  That is when the tonsils get so big, breathing is in danger.  In that setting, a course of steroids can shrink the swelling enough to improve breathing.

6.  Mono is also unique among viral infections for being able to cause the spleen to enlarge and to cause rather pronounced lethargy.

7. Key Point:  If your breathing is fine, your spleen not too big, and your lethargy manageable, mono is like any other cold, and so testing for it will not bring any added benefit.

Dr. Arthur Lavin

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