Diseases & Conditions

What is Tuberculosis?

What is tuberculosis (TB)?

TB is a disease caused by bacteria (Mycobacterium tuberculosis). It most commonly affects the lungs, although it can affect other parts of the body as well.

What is latent tuberculosis (LTBI)?  

Persons with LTBI are not infectious and cannot spread TB infection to others. They are usually well and do not have symptoms. They are infected with Mycobacterium tuberculosis, but do not have the TB disease. Those persons may develop TB disease if they do not receive treatment for their LTBI.

LTBI may be diagnosed by a blood test commonly called Quantiferon, otherwise by a skin test commonly called PPD.

Mode of transmission

The TB bacteria spreads through the air from a person who is ill with active TB. The bacteria are contained in small, airborne droplets created by coughing or sneezing.

In some people, especially those who have a weakened immune system, the TB bacteria become active, multiply, and cause TB disease, In this case, hospitalization and airborne precautions, such as wearing a protective N95 mask, are mandatory.


Symptoms of active TB may include:

  • Cough that lasts more than three weeks
  • Night sweats
  • Unintentional weight loss
  • Chest pain
  • Fever
  • Fatigue

Risk factors

Anyone can get TB, but some people are at an increased risk of being infected with TB bacteria if they:

  • Have spent time with a person with TB disease.
  • Are from a country or have visited areas where TB disease is very common.
  • Live or work where TB disease is more common, such as a homeless shelter, prison or jail or long-term care facility.
  • Are healthcare workers who work with patients or clients who are at an increased risk of getting TB disease.


The TB blood test (Quantiferon) measures how the immune system reacts to the bacteria that causes TB.

If the test is:

  • Positive: the person has been in contact or exposed to the TB bacteria. Additional tests are needed to determine if the person has LTBI or TB disease.
  • Negative: the person's blood did not react to the test, then LTBI or TB disease is less likely.


Treatment of LTBI (being a carrier and not contagious) is essential to prevent its progression to TB disease (being sick and contagious).

Once the diagnosis of LTBI has been made, you will meet with a physician who will recommend the most appropriate monitoring and/or any effective treatment regimen required to eradicate TB from your body.

This healthcare provider will also make every effort to ensure you complete the entire course of treatment for LTBI, if required.

© Copyright 2017 Cleveland Clinic Abu Dhabi. All rights reserved.

This information is provided by Cleveland Clinic Abu Dhabi, part of Mubadala Healthcare, and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition.

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