Tuberculosis (TB) Symptoms and Causes
Tuberculosis (TB) is a chronic bacterial infection that usually infects the lungs, although other organs 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, or exposed to, another person who is thought to have or does have TB. The exposed person will have a negative skin test, and 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/her body, but does not have symptoms of the disease. This person would have a positive skin test, but a normal chest X-ray.
- TB disease: This describes the person that has signs and symptoms of an active infection. The person would have a positive skin test and a positive chest X-ray.
The predominant TB bacterium is Mycobacterium tuberculosis (M. tuberculosis). Several people infected with M. tuberculosis never develop active TB. However, in people with weakened immune systems, especially those with HIV (human immunodeficiency virus), TB organisms can overcome the body's defenses, multiply and cause an active disease.