Tuberculosis, or TB, is one of the oldest and most common infectious diseases. About one third of the world population is believed to be infected with TB. Fortunately, only about 5 of these infections progress to active disease. The other 95 of infected people are said to have a dormant or latent infection they do not develop any symptoms, and do not transmit the disease. Tuberculosis is caused by a rodshaped bacterium, or a bacillus, called Mycobacterium tuberculosis. An infection is initiated following inhalation of mycobacteria present in aerosol droplets discharged into the atmosphere by a person.
With an active infection. The transmission process is very efficient as these droplets can persist in the atmosphere for several hours and the infectious dose is very low less than 10 bacilli are needed to start the infection. Once in the lung, the bacteria meet with the body’s firstline defense the alveolar macrophages. The bacteria are ingested by the macrophages but manage to survive inside. Internalization of the bacilli triggers an inflammatory response that brings other defensive cells to the area. Together, these cells form a mass of tissue, called a granuloma, characteristic.
Of the disease. In its early stage, the granuloma has a core of infected macrophages enclosed by other cells of the immune system. As cellular immunity develops, macrophages loaded with bacteria are killed, resulting in the formation of the caseous center of the granuloma. The bacteria become dormant but may remain alive for decades. This enclosed infection is referred to as latent tuberculosis and may persist throughout a person’s life without causing any symptoms. The strength of the body’s immune response determines whether an infection is arrested here or progresses to the next stage. In healthy.
Tuberculosis TB Progression of the Disease, Latent and Active Infections, Treatment.
People, the infection may be stopped permanently at this point. The granulomas subsequently heal, leaving small calcified lesions. On the other hand, if the immune system is compromised by immunosuppressive drugs, HIV infections, malnutrition, aging, or other factors, the bacteria can be reactivated, replicate, escape from the granuloma and spread to other parts of the lungs causing active pulmonary tuberculosis. This reactivation may occur months or even years after the initial infection. In some cases, the bacteria may also spread to other organs of the body via the lymphatic system or the bloodstream. This widespread.