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Tuberculosis – An Old Illness that Never Went Away

Recent events regarding the discovery of a couple of cases of Tuberculosis (TB) at a local High School serve to remind us that some diseases don’t ever really go away.  Many of us had nearly forgotten about TB.  At one time, most children got TB tests a number of times during their check up years.  Now, a TB test is no longer required  for most children before Kindergarten or going into college.  The old Tine Test that poked into our arms isn’t even used any more. It turns out that testing people who are at a low risk for TB, that is most children in the US, wasn’t very effective.

TB is an infection, usually in the lungs, that is caused by bacteria called Mycobacterium tuberculosis.  A healthy person, when exposed to this bacterium, may have only a mild illness or no symptoms.  However, as the person fights off the germ, it may simply be walled off, or locked up in a cyst in the lung, sometimes even too small to see on an x-ray.  At a later date, under stress of an illness or surgery or decreased immune function, the TB germ may “wake up” and cause a severe illness and allow spread to others through coughing or exposure to lung fluids.  TB is so contagious if not treated, in times past, people infected were sent to special hospitals and forced to live there so as to not spread the disease to others through coughing, etc.  With the advent of medicines to treat TB, we no longer need to isolate people once they have begun treatment.  As an aside, there are areas in the world, such as prisons in the former Soviet Union, where resistant strains of tuberculosis have emerged.

The way we look at TB these days is to worry less about populations at low risk and more about people who we think are at a higher risk for really having the disease.  These high risk people would include anyone who has had recent exposure (e.g. living with or working closely with) to someone who had active TB; people who recently moved from an area that is known to have a high TB rate; persons from homeless shelters and people who work in shelters, hospitals, prisons and nursing homes.  These are the people we need to be especially careful about testing.

The way to test for TB is with a test called a PPD – or also called a Mantoux (mantoo) test.  With this, a very tiny needle and a serum is used to raise up a little bump under the skin, usually on the forearm.  If a person has had exposure to the TB germ, the spot will swell up over the next 48-72 hours.  Depending on how much risk, the test is judged positive or negative based on how big the swelling is at that time.  If a person were in the lowest risk, the test would be considered negative even if the swelling were as big as 15mm (a little over ½ “). If, however, someone were in the group considered higher risk, such as a recent immigrant, the test would be called positive if it were over 5mm (< ¼ ”).  Once the test is called positive, the person must have a chest x-ray to look for any signs of active TB, and then begin a nine month course of daily medication.  This medication, called Isoniazid (INH) has some side effects such as nausea and lab work needs to be checked monthly to be sure it is not hurting the liver. While this may not seem so pleasant, it is the only way we have to decrease the chance of the latent or sleeping TB infection from becoming active and possibly spreading to others.  Once a person is taking medication to fight the germ, they are felt to be not infectious and may return to their usual daily activities.

For more information about Tuberculosis – check out http://www.aafp.org/afp/20000501/2681ph.html

Joseph Moore, PA-C

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