Tuberculosis is a chronic infectious disease predominantly caused by Mycobacterium tuberculosis. It is characterized by caseous necrosis that typically affects the lungs, but it can also affect other organs.

Description

Tuberculosis infections are caused by the Mycobacterium tuberculosis complex family consisting of many members, out of which the ones most commonly affecting humans include:

  • M. tuberculosis
  • M. bovis
  • M. africanum

Route of infection and progression

Person-to-person infections are spread through respiratory air droplets through coughing and sneezing.

Once the bacteria enters the body, most patients (75%) will be unaffected, but the remainder (25%) will become infected. This is known as the primary infection.

Once infected, they can go through several phases:

  • Progressive primary tuberculosis
  • Latent phase (dormant)
  • Secondary infection (reactivation/reinfection)
  • Healing
  • Progressive secondary tuberculosis

Most primary infections are asymptomatic and typically occur during childhood. In immune-competent patients, the primary infection will be followed by a latent (dormant) phase. Patients are not infectious during the primary and latent phases.

Secondary infection can appear

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