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Sravani.Kethireddy* et al. /International Journal Of Pharmacy&TechnologyIn many patients the infection waxes and wanes. Tissue destruction and necrosis are balanced byhealing and fibrosis. [24] Affected tissue is replaced by scarring and cavities filled with cheese-likewhite necrotic material. During active disease, some of these cavities are joined to the air passagesbronchi and this material can be coughed up. It contains living bacteria and can therefore pass oninfection. [24]STAGES OF INFECTION:There are several stages:• Primary infection• Latent infection• Active diseaseExcept for very young children and people with a weakened immune system, few people become sickimmediately after tuberculosis bacteria enter their body (this stage is called primary infection). In mostcases, tuberculosis bacteria that enter the lungs are immediately killed by the body's defenses. Thosethat survive are engulfed by white blood cells called macrophages. The engulfed bacteria can remainalive inside these cells in a dormant state for many years; walled off inside tiny scars (this stage iscalled latent infection). In 90 to 95% of cases, the bacteria never cause any further problems, but inabout 5 to 10% of infected people, they eventually start to multiply and cause active disease. At thisstage, infected people actually become sick and can spread the disease.More than half the time, dormant bacteria reactive within the first 2 years after the primary infection,but they may not reactivate for a very long time, even decadesThe progression of tuberculosis from latent infection to active disease varies greatly. Progression toactive disease is far more likely and much faster in people with HIV infection and other conditionsIJPT | June 2010 | Vol. 2 | Issue No.2 | 206-244Page 211