Tuberculosis (TB) is a bacterial infection caused by a germ called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but they can also damage other parts of the body. TB spreads through the air when a person with TB of the lungs or throat coughs, sneezes or talks. If you have been exposed, you should go to your doctor for tests. You are more likely to get TB if you have a weak immune system.
Tuberculosis (abbreviated as TB for tubercle bacillus or Tuberculosis) is a common and deadly infectious disease caused by mycobacteria, mainly Mycobacterium tuberculosis. Tuberculosis most commonly attacks the lungs (as pulmonary TB) but can also affect the central nervous system, the lymphatic system, the circulatory system, the genitourinary system, bones, joints and even the skin. Other mycobacteria such as Mycobacterium bovis, Mycobacterium africanum, Mycobacterium canetti, and Mycobacterium microti can also cause tuberculosis, but these species do not usually infect healthy adults.
Until 50 years ago, there were no medicines to cure TB. Now, strains that are resistant to a single drug have been documented in every country surveyed; what is more, strains of TB resistant to all major anti-TB drugs have emerged. Drug-resistant TB is caused by inconsistent or partial treatment, when patients do not take all their medicines regularly for the required period because they start to feel better, because doctors and health workers prescribe the wrong treatment regimens, or because the drug supply is unreliable.
A person can become infected with tuberculosis bacteria when he or she inhales minute particles of infected sputum from the air. The bacteria get into the air when someone who has a tuberculosis lung infection coughs, sneezes, shouts, or spits (which is common in some cultures). People who are nearby can then possibly breathe the bacteria into their lungs. You don’t get TB by just touching the clothes or shaking the hands of someone who is infected. Tuberculosis is spread (transmitted) primarily from person to person by breathing infected air during close contact.
TB is an increasing and major world wide problem, especially in Africa where the spread has been facilitated by AIDS. It is estimated that nearly 1 billion people will become newly infected, over 150 million will become sick, and 36 million will die worldwide between now and 2020 — if control is not further strengthened. Each year there are more than 9 million cases and close to 2 million deaths attributed to TB; 100,000 of those 2 million deaths occur among children.
Tuberculosis has plagued human beings for millennia. Signs of tubercular damage have been found in Egyptian mummies and in bones dating back at least 5,000 years. Today, despite advances in treatment, TB is a global pandemic, fueled by the spread of HIV/AIDS, poverty, a lack of health services and the emergence of drug-resistant strains of the bacterium that causes the disease.
Skin testing for tuberculosis is useful in countries where the incidence of tuberculosis is low, and the health care system works well to detect and treat new cases. In countries where BCG vaccination has been widely used, the TB skin test is not useful, because persons vaccinated with BCG will have a positive skin test.
TB infection means that MTB is in the body, but the immune system is keeping the bacteria under control. The immune system does this by producing macrophages that surround the tubercle bacilli. The cells form a hard shell that keeps the bacilli contained and under control. Most people with TB infection have a positive reaction to the tuberculin skin test. People who have TB infection but not TB disease are NOT infectious, i.e., they cannot spread the infection to other people. These people usually have a normal chest x-ray. TB infection is not considered a case of TB disease. Major similarities and differences between TB infection and TB disease are given in the table below.