Tuberculosis (TB) is a chronic bacterial infection that usually
infects the lungs, although other organs such as the kidneys,
spine, or brain are sometimes involved. TB is primarily an
airborne disease. There is a difference between being infected
with the TB bacterium and having active tuberculosis disease.
There are three important ways to describe the stages of TB.
They are as follows: - Exposure. This occurs when a person has
been in contact with, or exposed to, another person who is
thought to have or does have TB. The exposed person will have a
negative skin test, a normal chest X-ray, and no signs or
symptoms of the disease. - Latent TB infection. This occurs when
a person has the TB bacteria in his or her body, but does not
have symptoms of the disease. The infected person's immune
system walls off the TB organisms, and they remain dormant
throughout life in 90 percent of people who are infected. This
person would have a positive skin test but a normal chest X-ray.
- TB disease. This describes the per