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Learn About Tuberculosis

Tuberculosis (TB) is an airborne bacterial infection caused by the organism Mycobacterium tuberculosis that primarily affects the lungs, although other organs and tissues may be involved.

Key Points

  • It is not easy to become infected with tuberculosis.
  • Most infected people have latent TB, meaning they have the tuberculosis germs in their bodies, but their immune systems protect them from becoming sick and they are not contagious.
  • TB can almost always be treated and cured if you take medicine as directed.
  • There are forms of TB that are drug resistant.

What Is TB?

Tuberculosis (TB) is an infectious disease that usually attacks the lungs, but can attack almost any part of the body. Tuberculosis is spread from person to person through the air. When a person with TB in their lungs or throat coughs, laughs, sneezes, sings, or even talks, the germs that cause TB may spread through the air. If another person breathes in these germs there is a chance that they will become infected with tuberculosis.

It is important to understand that there is a difference between being infected with TB and having TB disease. Someone who is infected with TB has the TB germs, or bacteria, in their body. The body's immune system is protecting them from the germs and they are not sick. This is referred to as latent TB.
Someone with TB disease is sick and can spread the disease to other people. A person with TB disease needs to see a doctor as soon as possible. This is referred to as active TB.

There are also forms of TB that are drug resistant, or even worse—multi-drug resistant. This means that some of the drugs used to treat the infection are not effective against the resistant TB germs in the body. Learn more about the types of drug resistant TB.

How Does Someone Become Infected with TB?

It is not easy to become infected with tuberculosis. Usually a person has to be close to someone with TB disease for a long period of time. TB is usually spread between family members, close friends, and people who work or live together. TB is spread most easily in closed spaces over a long period of time.

How TB Affects Your Body

People with weakened immune systems (those with HIV/AIDS, those receiving chemotherapy, or children under 5 years old, for example) are at a greater risk for developing TB disease. When they breathe in TB bacteria, the bacteria settle in their lungs and start growing because their immune systems cannot fight the bacteria. In these people, TB disease may develop within days or weeks after the infection.
In other people, TB disease may develop months or years after the initial infection, at a time when the immune system becomes weak for other reasons and is no longer able to fight the bacteria.

When a person gets active TB disease, it means TB bacteria are multiplying and attacking the lung(s) or other parts of the body, such as the lymph nodes, bones, kidney, brain, spine, and even the skin. From the lungs, TB bacteria move through the blood to different parts of the body. Symptoms of active disease include cough, loss of weight and appetite, fever, chills and night sweats as well as symptoms from the specific organ or system that is affected; for example, coughing up blood or sputum in TB of the lungs, or bone pain if the bacteria have invaded the bones.

How Serious Is TB?

In some people, TB can cause cough, chest pain and bloody mucus. If it is not treated properly, TB can be fatal.

Despite popular misconceptions that tuberculosis (TB) is a disease of the past, it continues to pose a significant threat to public health.

Almost 2.2 billion people, or one third of the world's population, are infected with tuberculosis. Most infected people have latent TB, meaning they have the tuberculosis germs in their bodies, but their immune systems protect them from becoming sick. However, over 9.2 million people have active TB disease, worldwide. In the United States, TB is much less common, however, it continues to cause disproportionate illness in certain populations.

Learn more about causes, symptoms and risk factors.


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