Tuberculosis (TB) is a common and often deadly infectious disease caused by mycobacteria, usually ''Mycobacterium tuberculosis'' in humans. Tuberculosis usually attacks the lungs but can also affect other parts of the body. It is spread through the air, when people who have the disease cough, sneeze, or spit. Most infections in humans result in an asymptomatic, latent infection, and about one in ten latent infections eventually progresses to active disease, which, if left untreated, kills more than half of its victims.
Under a high magnification of 15549x, this colorized scanning electron micrograph (SEM) depicted some of the ultrastructural details seen in the cell wall configuration of a number of Gram-positive Mycobacterium tuberculosis bacteria. As an obligate aerobic organism M. tuberculosis can only survive in an environment containing oxygen. This bacterium ranges in length between 2 - 4 microns, and a width between 0.2 - 0.5 microns.
The classic symptoms are a chronic cough with blood-tinged sputum, fever, night sweats, and weight loss. Infection of other organs causes a wide range of symptoms. Diagnosis relies on radiology (commonly chest X-rays), a tuberculin skin test, blood tests, as well as microscopic examination and microbiological culture of bodily fluids. Treatment is difficult and requires long courses of multiple antibiotics. Contacts are also screened and treated if necessary. Antibiotic resistance is a growing problem in (extensively) multi-drug-resistant tuberculosis. Prevention relies on screening programs and vaccination, usually with Bacillus Calmette-Guérin vaccine.
A third of the world's population are thought to be infected with ''M. tuberculosis'', and new infections occur at a rate of about one per second. with many symptoms overlapping with other variants, while others are more (but not entirely) specific for certain variants. Multiple variants may be present simultaneously.
When the disease becomes active, 75% of the cases are pulmonary TB, that is, TB in the lungs. Symptoms include chest pain, coughing up blood, and a productive, prolonged cough for more than three weeks. Systemic symptoms include fever, chills, night sweats, appetite loss, weight loss, pallor, and often a tendency to fatigue very easily. This occurs more commonly in immunosuppressed persons and young children. Extrapulmonary infection sites include the pleura in tuberculosis pleurisy, the central nervous system in meningitis, the lymphatic system in scrofula of the neck, the genitourinary system in urogenital tuberculosis, and bones and joints in Pott's disease of the spine. An especially serious form is disseminated TB, more commonly known as miliary tuberculosis. Extrapulmonary TB may co-exist with pulmonary TB as well.
Studies utilizing DNA fingerprinting of ''M. tuberculosis'' strains have shown that reinfection contributes more substantially to recurrent TB than previously thought, with between 12% and 77% of cases attributable to reinfection (instead of reactivation).
Tuberculosis is one of the three primary diseases of poverty along with AIDS and malaria. The Global Fund to Fight AIDS was started in 2002 to raise finances to address these infectious diseases. Globalization has lead to increased opportunities for disease spread. In 2007, a tuberculosis scare occurred when Andrew Speaker flew on a transatlantic flight infected with multi-drug-resistant tuberculosis.
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