Tuberculosis (TB) is a bacterial infection caused by a bacterium called Mycobacterium tuberculosis. The bacteria usually attack the lungs but can also damage other parts of the body, such as the lymph nodes, kidneys, and bones. Mycobacterium tuberculosis can live only in people; it cannot be carried by animals, insects, soil, or other non-living objects.
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 (found worldwide).
A healthy immune system can help protect the body from an active TB infection, but the TB bacteria can lie dormant in the individual for years without producing symptoms.
When an individual is exposed to TB, macrophages (specialized white blood cells that ingest harmful organisms) begin to surround and "wall off" or encapsulate the TB bacteria in the lungs. If the macrophages are successful, the bacteria may remain within these capsules for years. The TB is alive in the body but in a dormant (in-active) state. These individuals are considered to have latent TB infection, and will test positive on the TB skin test. However, individuals with latent TB infection usually do not feel sick, do not have any symptoms, and cannot spread TB to others. However, some individuals with latent TB infection may eventually progress to active TB. About one in 10 individuals who have a latent TB infection go on to develop active TB sometime in their lifetime. When the immune system is weakened, such as in the elderly, infants, or those with human immunodeficiency virus (HIV), the chances of becoming ill from active TB are greater.
TB, in active form, is transmitted through airborne droplets. Individuals become infected with TB when they inhale particles of infected airborne saliva from the air. The bacteria become airborne when an infected person expels saliva (when they cough, sneeze, talk, spit, etc.).
Individuals with active TB disease can be treated if they seek medical help. Also, most individuals with latent TB infection can take medicine so that they will not develop active TB disease, and they will not become contagious.
Individuals with active TB typically receive a combination of antibiotics for several months to treat the infection. Commonly prescribed antibiotics include isoniazid/rifampin (Rifamate®), ethambutol (Myambutol®), and pyrazinamide.
Since active TB is slow to respond completely to therapy, prescribed medications must be taken every day for a long period of time. This may be for at least six months, and in some cases for a year or more. Left untreated, each individual with active TB disease will infect on average between 10-15 people every year.
Symptoms of active TB in the lungs may include a bad cough that lasts three weeks or longer, weight loss, coughing up blood or mucus, weakness or fatigue, night sweats, fever, and chills.
If not treated properly, the active form of TB can be deadly.
Someone in the world is newly infected with TB bacteria every second. According to the World Health Organization (WHO), overall, one-third of the world's population is infected with the TB bacteria. Every year, TB kills nearly two million people worldwide. Both the highest number of deaths and the highest mortality per capita are on the African continent.
The WHO estimates that 5-10% of people who are infected with TB (but who are not infected with HIV) become sick or infectious at some time during their life. Individuals with HIV and latent TB infection are much more likely to develop active TB.

Related Terms

Acquired immunodeficiency virus, active TB, AIDS, antibiotic, bacillus Calmette-Guerin, BCG, cancer, chemotherapy, corticosteroids, diabetes, drug resistance, extensively drug-resistant TB, fatigue, HIV, human immunodeficiency virus, immune system, immunity, latent TB, macrophage, malnutrition, Mantoux test, MDR-TB, meningeal TB, microbiology, microscopic-observation drug-susceptibility, miliary TB, MODS, multidrug-resistant TB, Mycobacterium tuberculosis,ototoxicity, pandemic, PPD, purified pork derivative, QuantiFERON-TB Gold test, recurrence, sputum, transmission, XDR-TB, x-ray.