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Ask the doctor: Do I need a tuberculosis test?

Q. Why is my doctor checking me for tuberculosis? I thought that was eradicated long ago

A. It would be wonderful if tuberculosis (TB) had been eradicated long ago, but unfortunately that’s not the case. It is true that the annual number of new cases in the United States has been dropping over the past 20 years; in 2013, there were about 9,500 new cases. However, around the world, particularly in developing nations, TB remains a huge problem. In 2013, there were nine million new cases of TB, and 1.5 million deaths from TB, in the world.

TB is an infectious disease, caused by a particular kind of bacteria. The infection usually is in the lungs, although it can spread to other parts of the body. It is highly contagious. A person with an active lung infection can spread the bacteria to other people by coughing into the air that others breathe.

When TB bacteria enter a person’s lungs for the first time, they often don’t cause any symptoms. They simply take up residence in the lung. They can remain there, unnoticed, for decades. Then, they can suddenly start multiplying and spreading—and make the person very sick.

Tuberculosis settles in the lungs. A person with the infection can spread the bacteria by coughing into the air.

Image: Thinkstock

The screening tests your doctor wants to do are designed to find out whether the bacteria quietly have entered your body. If so, they could “wake up,” multiply, and make you sick in the future. By treating them now, when they’re not causing symptoms, you can prevent ever getting sick.

When I entered medical school, many moons ago, we screened nearly everyone for TB. Since the number of people in the United States harboring TB bacteria has dropped greatly, today we perform screening tests only in people who are at somewhat increased risk. These include people who have been in close contact with others who have active TB infection, people who have lived in parts of the world where tuberculosis is much more common than in the United States, health care workers, people who work in prisons or homeless shelters, and people with weakened immune systems. That last group includes people with certain kinds of cancer, people with diabetes, people infected with HIV, people taking certain medications, people with kidney failure who are on dialysis, long-term smokers, people with a lung disease called silicosis, and people with a chest x-ray that shows a spot in the lung that could indicate a TB infection.

Because I’m a health care worker, I get screened for TB every year. I’m glad I do: it protects me against a disease that can be very serious. 

—Anthony L. Komaroff, M.D.
Editor in Chief
Harvard Health Letter

Posted by: Dr.Health

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