Tuberculosis

What is Tuberculosis (TB)?

Tuberculosis is caused by the bacterium Mycobacterium tuberculosis. The bacteria usually attack the lungs, but can attack other parts of the body such as the lymph nodes, kidneys, bones, or brain. Medications can treat TB, but if not recognized and treated, TB can progress and even be fatal. Identifying and treating those who are infected, but have not yet become ill with Active TB, can prevent the spread of TB.

How is TB transmitted?

Tuberculosis spreads through the air when a person with Active TB of the lungs coughs, sneezes, speaks, or sings. Bacteria in respiratory droplets can then be inhaled by others. It usually takes being in close proximity to a person with Active TB for prolonged periods of time in an enclosed environment to be at a higher risk for infection. TB is not as contagious as influenza.

TB is NOT spread by:

  • shaking someone's hand

  • sharing food or drink

  • touching bed linens or toilet seats

  • sharing toothbrushes

  • kissing

Does everyone exposed to TB become infected?

No. For many, their immune system is able to remove the bacteria, and they do not develop the disease. In other cases, the person’s immune response ”walls off” the bacteria inside the body, causing the bacteria to become dormant. The person does not develop Active TB during this time, and is said to have Latent TB infection (LTBI). The person is well and cannot spread the infection. If treated at this stage, Active TB can usually be prevented.

Active TB develops when the body can no longer keep the bacteria dormant. The bacteria become "active" and cause the person to become ill. This is called TB disease and may occur if LBTI is not fully treated, if a resistant strain of TB has developed, if the individual's immune system becomes weakened (e.g. cancer, HIV, malnutrition, diabetes, aging with subsequent weakening of the immune system, or long-term steroid use. Sometimes it occurs for unknown reasons.

Active TB develops when the body is no longer able to keep the bacteria dormant. In other words the bacteria become "active" and cause the person to become ill. This is called TB disease. It occurs for a variety of reasons such as: if LBTI is not fully treated, or if a resistant strain of TB has developed or if the individual's immune system becomes weakened (like with cancer, HIV, malnutrition, diabetes, or long-term use of steroids). It can also occur with aging and weakening of the immune system, or it may also occur for other, unknown reasons.

Is there a vaccine to prevent a person from getting TB?

A TB vaccine called Bacillus Calmette-Guerin (BCG) is given in many countries to prevent TB. Usually given to infants, it may be re-administered at other times. BCG offers protection against TB in children but typically does not offer protection into adulthood. It is not routinely used to prevent TB in the United States.

What are the symptoms of TB?

Latent TB- The person with LTBI has no symptoms

Active TB - Symptoms of TB disease depend on where in the body the TB bacteria are growing.

TB disease in the lungs (pulmonary TB) may cause:

  • A bad cough that lasts 3 weeks or longer

  • Coughing up blood or sputum (phlegm from deep inside the lungs)

Other symptoms of TB disease include:

  • Weakness or fatigue

  • Unexplained weight loss

  • No appetite

  • Fever and chills

  • Night sweats

How is tuberculosis diagnosed?

Latent TB infection (LTBI) can be diagnosed with a skin test or with a blood test:

Skin testing - This test, called a purified protein derivative (PPD) test, involves injecting a solution with a small amount of an inactivated portion of TB bacteria just beneath the surface of the skin, usually on the inside of the forearm. The person returns in 48-72 hours to have the reaction on the arm “read”. Most individuals previously infected with TB develop a red or swollen bump at the injection site. It usually takes 4 to 10 weeks after exposure to a person with Active TB for a PPD to become positive.

Blood tests - This test is known as an interferon gamma release assay (IGRA). Blood tests simplify TB testing, because they do not require a return trip to read the test reaction, and they are not affected by prior immunization with BCG vaccine. Two approved types provide similar results: Quantiferon Test (QFT) and the T-Spot. UHS uses the QFT.

Active TB is diagnosed by further testing of those with a positive test, and/or those with symptoms:

Chest x-ray to determine if a person has signs of past or Active TB.

Sputum evaluation and culture - to grow the bacterium to determine its sensitivities to TB medications. The person is referred to the TB Clinic for this evaluation.

Who should get tested for TB?

You should get tested for TB if:

  • They have been contacted by a health authority informing them that they’ve possibly been exposed to someone with TB; or

  • They have spent prolonged periods of time in close proximity in a closed environment with a person known or suspected to have TB disease; or

  • They have HIV infection or another condition that weakens their immune system and puts them at high risk for TB disease; or

  • They are from (or have spent an extended period in) a country where TB disease is common (e.g. most countries in Latin America, the Caribbean, Africa, Asia, Eastern Europe, and Russia); or

  • They live or have lived in the United States in a place where TB disease is more common, such as a homeless shelter, migrant farm camp, prison or jail, and some nursing homes; or

  • They inject or have injected illegal drugs; or

  • They have symptoms of TB disease.

What does one do if they think they have symptoms of TB?

People who think they have tuberculosis should consult a physician.

How is TB treated?

TB can almost always be treated and cured. It may require up to 9 months of therapy, depending on the medical regimen used. Those with TB disease need to take several different drugs, because multiple medications do a better job of killing all of the bacteria and preventing them from becoming resistant to medicines used to treat TB.

Courtesy of University Health Services, The University of Texas at Austin.
Published by the University of Texas at Austin University Health Services.
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
©2023 The University of Texas at Austin. All Rights Reserved.