Tuberculosis is still a killer disease
Q: Why does my doctor want to test me for tuberculosis? I thought that was eradicated a long time ago.
A: It would be wonderful if tuberculosis (TB) had been eradicated long ago. Unfortunately, that's not the case.
The annual number of new cases in the United States has been dropping over the past 20 years. However, around the world, particularly in developing nations, TB remains a huge problem. More than 1 million people die of TB each year.
TB is an infectious disease, caused by a particular kind of bacteria. The infection usually attacks the lungs, although it can spread to other parts of the body. It is highly contagious. TB bacteria are spread from person to person through the air, in droplets of secretions that come out of your mouth or nose when you cough or sneeze. (I've put an illustration on my website, AskDoctorK.com.)
When TB bacteria enter a person's lungs for the first time, they often don't cause any symptoms. At this point, the immune system usually can keep the bacteria from multiplying. But it cannot destroy them completely.
The bacteria can remain in the lungs, inactive and unnoticed, for decades. (People with an inactive infection are not contagious.) However, in the future, the bacteria can suddenly start to multiply and spread - and make the person very sick. This happens when the immune system is weakened, such as by another disease, or by immune-suppressing treatments.
The only way to tell if a person has an inactive infection is with a TB skin test. (It is also called the "Mantoux tuberculin" skin test.) If the test indicates that you do have a silent TB infection, you will need to take a combination of four drugs for about six months. By treating the TB now, when it's not causing symptoms, you can greatly reduce the risk of ever getting sick.
When I entered medical school, we screened nearly everyone for TB. Since then, the number of people in the U.S. 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 an active TB infection, people who have lived in parts of the world where TB is common, health care workers, people who work in prisons or homeless shelters, and people with weakened immune systems.
I get screened for TB every year because I'm a health care worker. When I was very young, a person close to me had active TB. That was before there were good antibiotics to treat TB. Fortunately, tests showed that the TB bacteria never entered my body when I was young. But I still get retested each year because all health care workers are at risk of being exposed to new TB infections.
In my medical career, I've also taken care of quite a number of patients with active TB who were coughing, but fortunately they also did not pass the bacteria to me. I'm glad I get a regular screening, as it protects me against a disease that can be very serious.
• Dr. Anthony Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.