Tuberculosis (TB) is a serious disease that spreads through the air. It is caused by a bacterium called Mycobacterium tuberculosis. Tuberculosis usually affects the lungs. However, it can affect other parts of the body, such as the central nervous system. About 10-15 million Americans are infected with tuberculosis. For most people with healthy immune systems, this is not a problem. Nine out of 10 of them won't develop active disease with symptoms.
The risk is great, however, for people who are HIV-positive. That's because tuberculosis takes advantage of a weakened immune system, which is why it's called an opportunistic infection. Worldwide, tuberculosis is the leading cause of death for people infected with HIV (human immunodeficiency syndrome). If you are HIV-positive, you should be tested for tuberculosis. Prevention and treatment not only help control tuberculosis, but also help prevent greater damage to your immune system.
CD4 cells are a type of white blood cell that fights infection. Another name for them is T-helper cells. CD4 cells are made in the spleen, lymph nodes, and thymus gland, which are part of the lymph or infection-fighting system. CD4 cells move throughout your body, helping to identify and destroy germs such as bacteria and viruses.
The CD4 count measures the number of CD4 cells in a sample of your blood drawn by a needle from a vein in your arm. Along with other tests, the CD4 count helps tell how...
The bacteria that cause tuberculosis travel through the air, such as in a cough or sneeze. But you are not likely to get the disease through a single exposure. And you can't get it from sharing dishes or utensils, or through touching someone who has it.
You are more likely to get tuberculosis from constant exposure to an infected person, such as someone with whom you work or live. You are likely to get tuberculosis in places with poor ventilation or crowded conditions. If you are HIV-positive, discuss with your doctor whether it is safe to continue working in places like: