Tuberculosis (TB) is an infection caused by Mycobacterium tuberculosis, a bacterium that thrives in oxygen. For this reason, TB disease is most commonly seen in the lungs, although it can also occur in other organs.
Tuberculosis is spread through the air by someone with the lung form of the disease. That person coughs or breathes the germ out, and it can remain in the air for several hours. Other people who walk through that air can then breathe the germ in. Because of the way TB is transmitted, good ventilation decreases the chance of infection; it is more likely to get TB in an elevator than on a street corner. The bacterium is also killed by UV light, so it cannot survive in sunlight. This also makes outdoor transmission very rare.
If a person breathes the bacteria in at a time when he or she is healthy, the immune system encapsulates the bacteria. Although the person has no symptoms and is not contagious, he or she may develop TB disease in the future.
In 90% of cases, the immune system is able prevent TB symptoms when the person first comes in contact with the bacteria. Because of this, most people would never know that they have been infected unless they have a skin test. After the infection is confirmed, a chest x-ray determines if the disease is active in the body.
People with TB infection may show no signs of the disease. They cannot spread the infection. On the other hand, people with TB disease are contagious, and may experience the following symptoms:
Once on medications, people with TB disease become less and less contagious with each dose. In fact, individuals become non-contagious long before they complete their therapy and are cured. People who test positive for TB infection and do not show signs of the disease can also be treated with medication to rid themselves of the bacteria.
For more information about TB, contact The Miriam Hospital's RISE Clinic at 401-793-2427.