What Is Tuberculosis?
Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis that usually affects the lungs. It is not very common in the U.S., but it still remains a leading cause of death in other parts of the world.
Not everyone infected with tuberculosis becomes sick, so there are two TB-related conditions:
- Latent TB infection
- The body is able to fight the bacteria
- The person has no symptoms
- Cannot spread TB to others
- Will usually have a positive TB skin test reaction or positive TB blood test
- May develop TB disease if treatment is not received for latent TB infection
- TB disease
- Patients are sick and have symptoms
- The bacteria can be spread to others from the infected patient
- The risk of developing TB disease is higher in people who have weakened immune systems
What Causes Tuberculosis?
Tuberculosis is caused by a bacterium called Mycobacterium tuberculosis. The bacteria are spread through respiratory droplets propelled into the air when a person sick with tuberculosis coughs or sneezes.
Rarely, tuberculosis may be spread by eating or drinking something infected with tuberculosis, such as unpasteurized milk from an animal with TB.
Risk factors for developing tuberculosis include:
- Being a health care or laboratory worker who has contact with patients with active TB disease
- Known exposure to someone with active TB
- Birth or extended stay in a part of the world where TB is common
- Taking medications that weaken the immune system, such as steroids or medications for rheumatoid arthritis
- HIV infection
How Is Tuberculosis Diagnosed?
Tuberculosis is diagnosed with the following tests:
- Tuberculin skin test (sometimes also called a purified protein derivative test [PPD])
- The patient receives a shot in the arm that contains tiny pieces of dead TB bacteria
- Two to three days later, the spot where the shot was given is examined to see if there is a skin reaction (redness or swelling) and the extent of the reaction
- Skin tests are usually positive within 4 to 10 weeks after exposure
- Blood test (interferon-gamma release assays [IGRAs])
- Blood tests are available in many areas, but not everywhere
Latent tuberculosis infection is diagnosed with a positive skin test or blood test, followed by a clinical evaluation and imaging such as a chest X-ray to make sure the TB is not active and causing disease.
What Is the Treatment for Tuberculosis?
Tuberculosis can be cured; however, it is important that patients take all medicines for the duration they are prescribed, exactly as prescribed. If patients stop taking medications before the course is finished, or they do not take the medications as directed, they can become sick again and they may be resistant to the initial medications. Drug-resistant TB is harder and more expensive to treat. Untreated tuberculosis can be deadly.
Treatment for latent tuberculosis infection usually lasts 3 months or longer and includes:
- There are several different drug regimens
- Avoid alcohol and acetaminophen (Tylenol), both of which can make the liver work harder, potentially increasing the risk of liver injury from TB medications
- People treated for latent TB infection are usually monitored once monthly by a doctor to check for medication toxicity, such as liver damage
Treatment for active tuberculosis disease usually lasts 6 to 9 months and includes:
What Are Complications of Tuberculosis?
Untreated tuberculosis can be fatal. Complications of tuberculosis include:
How Do You Prevent Tuberculosis?
There is a tuberculosis vaccine called Bacillus Calmette-Guérin (BCG) that is given in many countries to prevent infection with TB, however, BCG is not routinely used to prevent TB in the U.S.
If you have been diagnosed with latent tuberculosis infection and you are in a high-risk group for developing active TB disease, medication should be taken to prevent development of TB disease.
Tuberculosis is much more common in other parts of the world than it is in the U.S. Travelers to parts of the world where TB is endemic are advised to avoid close contact or prolonged time with known TB patients in crowded, enclosed environments such as clinics, hospitals, prisons, or homeless shelters.