Tuberculosis (commonly abbreviated to TB, short for tubercle bacillus) encompasses an enormously wide disease spectrum affecting multiple organs and body systems predominantly caused by the organism Mycobacterium tuberculosis. A small proportion can also be caused by Mycobacterium bovis.
Although tuberculosis continues to be very common in developing nations. Approximately 10 million people globally per year have positive exposure to tuberculosis . In Western industrialised populations it has become uncommon but is increasing in prevalence among immunocompromised patients, particularly those with HIV/AIDS. An estimated 5% HIV patients have Mycobacterium tuberculosis infections, which become clinically apparent when CD4+ counts drop to below 350 cells/mm, typically with findings of post-primary pulmonary tuberculosis .
Clinical presentation will depend upon the morphology of infection and location. These are discussed in separate articles.
History and etymology
Aristotle is usually credited as being the first to recognize the contagious nature of the disease. Discovery of the specific infectious agent, the tubercle bacillus (Mycobacterium tuberculosis), did not occur for several millennia until it was isolated by Robert Koch in 1882 . M. tuberculosis was previously known as Koch bacillus and tuberculosis known as Koch disease. It was also historically known as consumption due to the severe associated weight loss.