What Is TB?
TB, or tuberculosis, is a disease caused by bacteria called Mycobacterium tuberculosis. The bacteria can attack any part of your body, but they usually attack the lungs. TB disease was once the leading cause of death in the United States.
In the 1940s, scientists discovered the first of several drugs now used to treat tuberculosis. As a result, tuberculosis slowly began to disappear in the United States. But tuberculosis has come back. After 1984, the number of tuberculosis cases reported in the United States began to increase. More than 25,000 cases were reported in 1993.
TB is spread through the air from one person to another. The bacteria are put into the air when a person with tuberculosis disease of the lungs or throat coughs or sneezes. People nearby may breathe in these bacteria and become infected.
People who are infected with tuberculosis do not feel sick, do not have any symptoms, and cannot spread TB. But they may develop tuberculosis disease at some time in the future. People with tuberculosis disease can be treated and cured if they seek medical help. Even better, people who have tuberculosis infection but are not yet sick can take medicine so that they will never develop tuberculosis disease.
This booklet answers common questions about tuberculosis. Please ask your doctor or nurse if you have other questions about tuberculosis infection or tuberculosis disease.
How Is Tuberculosis Spread?
TB is spread through the air from one person to another. The bacteria are put into the air when a person with tuberculosis disease of the lungs or throat coughs or sneezes. People nearby may breathe in these bacteria and become infected.
When a person breathes in tuberculosis bacteria, the bacteria can settle in the lungs and begin to grow. From there, they move through the blood to other parts of the body, such as the kidney, spine, and brain.
TB in the lungs or throat can be infectious. This means that the bacteria can be spread to other people. TB in other parts of the body, such as the kidney or spine, is usually not infectious.
People with tuberculosis disease are most likely to spread it to people they spend time with every day. This includes family members, friends, and coworkers.
What Is Tuberculosis Infection?
In most people who breathe in tuberculosis bacteria and become infected, the body is able to fight the bacteria to stop them from growing. The bacteria become inactive, but they remain alive in the body and can become active later. This is called tuberculosis infection. People with tuberculosis infection- have no symptoms
- don't feel sick
- can't spread TB to others
- usually have a positive skin test reaction
- can develop TB disease later in life if they do not receive preventive therapy
Many people who have tuberculosis infection never develop tuberculosis disease. In these people, the TB bacteria remain inactive for a lifetime without causing disease. But in other people, especially people who have weak immune systems, the bacteria become active and cause tuberculosis disease.
What Is Tuberculosis Disease?
TB bacteria become active if the immune system can't stop them from growing. The active bacteria begin to multiply in the body and cause tuberculosis disease. Some people develop TB disease soon after becoming infected, before their immune system can fight the tuberculosis bacteria. Other people may get sick later, when their immune system becomes weak for some reason.Babies and young children often have weak immune systems. People infected with HIV, the virus that causes AIDS, have very weak immune systems. Other people can have weak immune systems, too, especially people with any of these conditions:
- substance abuse
- diabetes mellitus
- silicosis
- cancer of the head or neck
- leukemia or Hodgkin's disease
- severe kidney disease
- low body weight
- certain medical treatments (such as corticosteroid treatment or organ transplants)
Symptoms of tuberculosis depend on where in the body the tuberculosis bacteria are growing. TB bacteria usually grow in the lungs. TB in the lungs may cause
- a bad cough that lasts longer than 2 weeks
- pain in the chest
- coughing up blood or sputum (phlegm from deep inside the lungs)
Other symptoms of tuberculosis disease are
- weakness or fatigue
- weight loss
- no appetite
- chills
- fever
- sweating at night
For information on how TB disease is treated, see the section on tuberculosis disease.
