Mycobacterium tuberculosis bacteria cause the treatable infection tuberculosis (TB). TB typically occurs in the lungs but can affect any part of the body. Not everyone with TB becomes sick.  Symptoms of the disease include cough, fatigue, weight loss, fever and night sweats.

TB has 2 stages—latent TB infection (LTBI) and active TB disease.  Many people with LTBI never develop active TB disease. Others progress from LTBI to active TB disease—often due to a weakened immune system.  Active TB disease is life-threatening.

Active TB disease

  • May show symptoms.
  • May feel ill.
  • May be contagious.
  • Have positive TB test results.
  • If TB is in their lungs, will have abnormal chest x-rays.
  • Need treatment to be cured


  • Do not show symptoms.
  • Do not feel ill.
  • Not contagious.
  • May have positive TB skin reaction and blood tests.
  • Usually have normal chest x-ray.
  • May develop active TB disease, if left untreated.