Tuberculosis
Tuberculosis is a common and deadly infectious disease caused by the mycobacterium Mycobacterium tuberculosis or Mycobacterium bovis, which most commonly affects the lungs (pulmonary TB) but can also affect the central nervous system, lymphatic system, circulatory system, genitourinary system, bones, joints, and even the skin.
Over one-third of the world's population now has the TB bacterium in their bodies and new infections are occurring at a rate of one per second. Not everyone who is infected develops the disease and asymptomatic latent TB infection is most common. However, one in ten latent infections will progress to active TB disease which, if left untreated, will kill more than half of its victims. In 2004, 14.6 million people had active TB and there were 8.9 million new cases and 1.7 million deaths, mostly in developing countries. A rising number of people in the developed world contract tuberculosis because their immune systems are compromised by immunosuppressive drugs, substance abuse, or HIV/AIDS.
In the patients where TB becomes an active disease, 75% of these cases affect the lungs, where the disease is called pulmonary TB. Symptoms include a productive, prolonged cough of more than three weeks duration, chest pain, and coughing up blood. Systemic symptoms include fever, chills, night sweats, appetite loss, weight loss, paling, and those afflicted are often easily fatigued.
When the infection spreads out of the lungs, extrapulmonary sites include the pleura, central nervous system in meningitis, lymphatic system in scrofula of the neck, genitourinary system in urogenital tuberculosis, and bones and joints in Pott's disease of the spine. An especially serious form is disseminated, or miliary tuberculosis. Extrapulmonary forms are more common in immunosuppressed persons and in young children. Infectious pulmonary TB may co-exist with extrapulmonary TB, which is not contagious.
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Tuberculosis
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