18.02.06 - 9:04 a.m.


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.

What Happens


Tuberculosis (TB) develops when Mycobacterium tuberculosis bacteria are inhaled into the lungs. The infection usually stays in the lungs, but the bacteria can travel through the bloodstream to other parts of the body (extrapulmonary TB).

An initial (primary) infection can be so mild that you don't even know you have an infection. In a person who has a healthy immune system, the body usually fights the infection by walling off (encapsulating) the bacteria into tiny capsules called tubercles. The bacteria remain alive but cannot spread to surrounding tissues or other people. This stage is called latent TB, and most people never go beyond it.

A positive reaction to a tuberculin skin test is how most people find out they have latent TB. It takes about 48 hours after the test for a reaction to develop, which is usually a red bump where the needle went into the skin. Or you could have a blood test (QuantiFERON-TB Gold) that provides results in about 24 hours.

If a person's immune system becomes unable to prevent the bacteria from growing, the TB becomes active. Of people who have latent TB, 5% (1 person in 20) will develop active TB within 2 years after the initial infection. Another 5% of people who have latent TB will develop active TB at some point in their life.1

People who have latent TB may be at risk for developing the active disease if they:

Have a condition or disease that weakens their immune system, such as human immunodeficiency virus (HIV) infection, some cancers, or poorly controlled diabetes.
Have poor access to health care, such as homeless people, migrant farm workers, or people who abuse alcohol or drugs.
Take medications that contain corticosteroids for a long time.
Have a condition that results in an impaired immune system, which can occur in older adults, newborns, women who have recently given birth, or people who have had an organ transplant and are taking medications to prevent organ rejection.
Have a chronic lung disease caused by inhaling sand-like dust (silicosis).
Are 10% or more under their healthy body weight.




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