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Tuberculosis (TB)

Topic Overview

What is tuberculosis?

Tuberculosis (TB) is a bacterial infection that is most often found in the lungs (pulmonary TB) but can spread to other parts of the body (extrapulmonary TB). TB in the lungs is easily spread to other people through coughing or laughing. Treatment is often successful, though the process is long. Treatment time averages between 6 and 9 months.

Tuberculosis is either latent (dormant) or active.

  • Latent TB means that you have the TB-causing bacteria in your body, but you cannot spread the disease to others. However, you can still develop active TB.
  • Active TB means the infection is spreading in your body and, if your lungs are infected, you can spread the disease to others.

What causes tuberculosis?

Tuberculosis is caused by Mycobacterium tuberculosis, slow-growing bacteria that thrive in areas of the body that are rich in blood and oxygen, such as the lungs.

What are the symptoms of tuberculosis?

If you have latent TB, you will not have symptoms unless the disease becomes active. Most people don’t know that they have latent TB.

Symptoms of active TB may include:

  • Ongoing cough that brings up thick, cloudy, and sometimes bloody mucus (sputum) from the lungs.
  • Fatigue and weight loss.
  • Night sweats and fever.
  • Rapid heartbeat.
  • Swelling in the neck (when lymph nodes in the neck are infected).
  • Shortness of breath and chest pain (in rare cases).

Sometimes, when you are first infected, the disease is so mild you don’t know you have it. This is also true for people with latent TB because they have no symptoms.

How is TB spread to others?

People who have a latent TB infection cannot spread the disease.

TB in the lungs (pulmonary TB) is contagious. It spreads when a person who has active disease exhales air that contains TB-causing bacteria and another person inhales the bacteria from the air.

TB in other areas of the body (extrapulmonary TB) cannot spread easily to others.

How is TB diagnosed?

Latent TB is often discovered when you have a positive reaction to a tuberculin skin test or blood test. Active TB is diagnosed by finding the TB-causing bacteria in a sputum sample (fluid from the lungs) or in samples from other parts of the body. Doctors sometimes use a chest X-ray to help diagnose active TB.

Extrapulmonary TB is diagnosed by a biopsy and culture, CT scan, or MRI.

How is TB treated?

Doctors generally use a combination of 4 antibiotics to treat active TB, whether it occurs in the lungs or elsewhere. Medications for active TB must be taken for at least 6 months. Almost all people who take their medications as directed are cured. If tests continue to show positive results, treatment is extended for 8 to 9 months.

One antibiotic taken for 9 months is the usual treatment for latent TB. This prevents the infection from becoming active and reduces the risk of complications.

If you miss doses of medication or you stop treatment too soon, your treatment may go on longer or you may have to start over. This can also cause the infection to get worse or lead to antibiotic-resistant infections that are much harder to treat.

A health professional may have to watch you take your medications. This may mean daily visits to a doctor’s office or public health facility, or you may have home visits. A cure for TB requires you to take all doses of the antibiotics. Direct observational treatment ensures that people follow medication instructions, which is helpful because of the long treatment course for TB. Cure rates for TB have greatly improved because of this treatment practice.

If active TB is not treated, it can damage the lungs or other organs and can possibly cause death.


If you have latent tuberculosis (TB), you do not have symptoms and cannot spread the disease to others. If you have active TB, you do have symptoms and can spread the disease to others. Which specific symptoms you have will depend on whether your TB infection is in your lungs (the most common site) or in another part of your body (extrapulmonary TB).

There are other conditions with symptoms similar to TB, such as pneumonia or lung cancer.

Symptoms of active TB in the lungs

Symptoms of active TB in the lungs begin gradually and develop over a period of weeks or months. You may have one or two mild symptoms and not even know that you have the disease.

Common symptoms may include:

  • A cough with thick, cloudy, and sometimes bloody mucus (sputum) from the lungs for more than 2 weeks.
  • A rapid heartbeat.
  • A swollen neck (when lymph nodes in the neck are infected).

Other symptoms may include:

  • Fever, chills, and night sweats.
  • Fatigue and muscle weakness.
  • Loss of appetite and unexplained weight loss.
  • Shortness of breath and chest pain (in rare cases).

Symptoms of an active TB infection outside the lungs

Symptoms of TB outside the lungs (extrapulmonary TB) vary widely depending on which area of the body is infected. For example, back pain can be a symptom of TB in the spine.

When To Call a Doctor

Call your doctor immediately if you have:

  • Symptoms (such as an ongoing cough with fever, fatigue, and weight loss) that could be caused by tuberculosis (TB).
  • Been in close contact with someone who has untreated active TB, which can be spread to others, or you have had lengthy close contact with someone you think has untreated active TB.
  • Blurred vision or color blindness and are taking ethambutol for TB.
  • Yellowing of your skin and the whites of your eyes (jaundice) or you have abdominal pain and you are taking isoniazid or other medications for TB.

Call your doctor if you:

  • Have recently had a TB skin test and you have a red bump at the needle site. You need to have a reaction measured by a health professional within 2 to 3 days after the test. This measurement is important in deciding whether you need more tests or treatment.



Watchful Waiting

Watchful waiting is a wait-and-see approach. If you get better on your own, you won’t need treatment. If you get worse, you and your doctor will decide what to do next.

If you have symptoms of TB (an ongoing cough with fever, fatigue, and weight loss), you should not wait to get treatment. Contact your doctor or other health professional as soon as possible.

If you have been exposed to someone who has active TB, don’t wait to see if you develop symptoms. Contact your doctor or other health professional to get a tuberculosis skin test.


Avoid getting active TB

Active tuberculosis (TB) is an infection that is spreading in a person’s body, and it is very contagious.

The World Health Organization (WHO) estimates that one-third of the world’s population is infected with the bacteria that causes TB. To avoid getting an active TB infection:

  • Do not spend long periods of time in stuffy, enclosed rooms with anyone who has active TB until that person has been treated for at least 2 weeks.
  • Use protective measures, such as face masks, if you work in a facility that cares for people who have untreated TB.
  • Ask your doctor how to prevent TB from spreading to others if you live with someone who has active TB. Help and encourage the person who has TB to follow the treatment instructions.


Prevent latent TB from becoming active

Usually, treatment with isoniazid for about 9 months or rifampin for 6 months can prevent a latent TB infection from developing into active TB. Treatment is recommended for anyone who has a positive skin and is especially important for people who:

  • Are known to or are likely to be infected with the human immunodeficiency virus (HIV).
  • Have close contact with a person who has active TB.
  • Have a chest X-ray that suggests a TB infection, and they have not had a complete course of treatment.
  • Inject illegal drugs.
  • Have a medical condition or take medications that weaken the immune system.
  • Have had a tuberculin skin test within the past 2 years that was negative but now have a positive test.

Credits for Tuberculosis (TB)

Author Nancy Bateman
Editor Kathleen M. Ariss, MS
Associate Editor Michele Cronen
Associate Editor Lisa Shaw
Primary Medical Reviewer Martin Gabica, MD
– Family Medicine
Specialist Medical Reviewer Lee B. Reichman, MD, MPH
– Internal Medicine, Pulmonology
Last Updated May 25, 2005

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