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TB disease is an infection which most commonly affects the lungs, where it is called pulmonary TB. But it can also affect the central nervous system ( meningitis), lymphatic system, circulatory system (miliary TB), genitourinary system, and bones and joints.
TB is caused by the bacterium Mycobacterium tuberculosis. It is the most common major infectious disease today, infecting two billion people or one-third of the world's population, with nine million new cases of active disease annually, resulting in two million deaths, mostly in developing countries.
Most of those infected (90 percent) have asymptomatic latent TB infection (LTBI). There is a 10 percent lifetime chance that LTBI will progress to active TB disease which, if left untreated, will kill more than 50 percent of its victims. TB is one of the top three infectious killing diseases in the world: HIVThe Human immunodeficiency virus HIV is a frequently mutating retrovirus that attacks the human immune system and which has been shown to cause acquired immune deficiency syndrome (AIDS). History HIV was discovered and identified as the agent for AIDS by/ AIDSAIDS Acquired Immunodeficiency Syndrome or Acquired Immune Deficiency Syndrome sometimes written Aids is a human disease characterized by progressive destruction of the body's immune system. It is widely accepted that AIDS results from infection with HIV kills 3 million people each year, TB kills 2 million, and malariaMalaria ( Italian: bad air ; formerly called ague or marsh fever in English) is an infectious disease which causes about 500 million infections and 2 million deaths annually, mainly in the tropics and sub-Saharan Africa. The protozoan cause of malaria was kills 1 million.
The neglect of TB control programs, HIV/AIDS, and immigration has caused a resurgence of tuberculosis. Multiple drug resistant strains of MDR-TB is increasing. The World Health OrganizationFor other meanings of the acronym 'WHO', see WHO (disambiguation : Please note ''Sections of this article have been edited by a user in arbitration. The relevance of those sections is controversial but they may remain whilst the arbitration is in process declared TB a global health emergency in 1993.
Acid-fast bacilli (AFB) (shown in red) are tubercle bacilli Mycobacterium tuberculosis. The cause of tuberculosis, Mycobacterium tuberculosis (MTB), is a slow-growing Gram-positiveGram-positive bacteria are those that are stained dark blue or violet by gram staining, in contrast to gram-negative bacteria, which are not effected by the stain. The stain is caused by a high amount of peptidoglycan in the cell wall, which typically lac aerobicAn aerobic organism or aerobe is an organism that has an oxygen based metabolism. Aerobes, in a process known as cellular respiration, use oxygen to oxidize substrates (for example sugars and fats) in order to obtain energy. A good example would be the ox bacterium that divides every 16 to 20 hours. This is extremely slow compared to other bacteria which tend to have division times measured in minutes (among the fastest growing bacteria is a strain of E. coli that can divide roughly every 20 minutes). It is a small rod-like bacillus which can withstand weak disinfectants and can survive in a dry state for weeks but, spontaneously, can only grow within a host organism (in vitro culture of M. tuberculosis took a long time to be achieved, but is nowadays a normal laboratory procedure).
MTB is identified microscopically by its staining characteristics: it retains certain stains after being treated with acidic solution, and is thus classified as an " acid-fast bacillus " or "AFB". In the most common staining technique, the Ziehl-Neelsen stain, AFB are stained a bright red which stands out clearly against a blue background. Acid-fast bacilli can also be visualized by fluorescent microscopy, and by auramine-rhodamine stain.
The M. tuberculosis complex includes 3 other mycobacteria which can cause tuberculosis: M. bovis, M. africanum, and M. microti. The first two are very rare causes of disease and the last one does not cause human disease.
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