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The Informed Parent

Questions & Answers: Tuberculosis

by Louis P. Theriot, M.D., F.A.A.P.
Published on Jan. 01, 2000

Question: I have a 9 year old son. I just found out that his best friend has a positive T.B. skin test. He apparently had a normal chest x-ray, and has to take a medication for 9 months. His mom assured me that I didn't have to worry about my son. I am a bit concerned. What is T.B.? Should I have my son tested anyway?

Answer: Tuberculosis (TB) is an infection that is caused by the bacteria Mycobacterium tuberculosis. It can infect virtually any organ of the body, however, the main organ system affected are the lungs (pulmonary TB). In pulmonary TB, there can be enlarged lymph nodes in the chest, pneumonia, collapse or scarring of certain portions of the lungs, and even holes or "cavitations" of the lung tissue. It can be a serious and devastating disease. Other organs that can become infected with TB include the kidneys, joints, bones and skin. It can also cause meningitis.

The primary way in which TB is spread is through tiny droplets that spread when a person with active disease coughs or sneezes. A person can therefore become infected the checkout line of the market, in a theater, in a restaurant etc..

TB is found in all communities of the United States. Although there had been a decline in the number of cases reported in the U.S. over the past two decades, the number has leveled off and may actually be on the rise. This may be due, in part, to the large number of immigrants each year.

The TB skin test that you referred to is the main tool that we have to diagnose TB. A positive skin test means that a person has become "infected". This means that his immune system has been turned on to recognize the TB bacteria. It does not mean that a person has the active disease or is contagious. A chest x-ray is needed to determine this.

If a person has a positive skin test and a normal chest x-ray, they are infected, but without active disease. They are not infectious to others. This person should receive 6-9 months of a single medication, called isoniazid. This should provide adequate protection from the disease becoming active for at least 20 years. One must remember that the skin test may remain positive for the rest of that person's life.

On the other hand, if a person has a positive skin test AND an abnormal chest x-ray, they are considered to have active disease and need to be treated with multiple drugs. They are highly contagious for at least the first 2-4 weeks of their therapy.

From what you have indicated, it sounds as if your son's friend falls into the first category: infected but without active disease. If so, he is in no way contagious and should pose no risk to your son. You should clarify this with his mother and ask your doctor if you have any questions.

There is no reason to have your son skin tested just because of his friend. He should be tested though, on a regular basis as part of his on-going well care. Our pediatric practice is in Southern California and there is a large immigrant population. We perform skin testing on all of our patients every two years.

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