TB is a disease caused by bacteria called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but can also attack any part of the body such as the kidney, spine, and brain. TB disease can be fatal, but the good news is, TB can be cured!
TB is spread through the air from one person to another. Only persons who are sick with TB in their lungs are infectious. The bacteria are put into the air when a person with active TB disease of the lungs or throat coughs, sneezes, talks or spits. People nearby may breathe in these bacteria and may likewise become infected.
However, not everyone infected with TB bacteria becomes sick. People who are not sick have what is called latent TB infection. These people may not feel sick, do not have any symptoms, and cannot spread TB to others. However, some people with latent TB infection go on to get TB disease.

People with active TB disease can be treated and cured if they seek medical help. Additionally, people with latent TB infection can take medicine so that they will not develop active TB disease.

How is TB spread?

TB is spread through the air from one person to another. The bacteria are put into the air when a person with active TB disease of the lungs or throat coughs or sneezes. People nearby may breathe in these bacteria and become infected.

When a person breathes in TB bacteria, the bacteria can settle in the lungs and begin to grow. From there, they can move through the blood to other parts of the body, such as the lymph nodes, 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 active TB disease are most likely to spread it to people they spend time with every day. This can include family members, friends, and co-workers.

What is latent TB infection?

In many people who breathe in TB bacteria and become infected, the body is able to fight the bacteria. Sometimes, the bacteria become inactive, but can remain alive in the body and can become active later. This is called latent TB infection. People with latent TB infection:
• have no symptoms
• Do not feel sick
• cannot spread TB to others
• usually have a “positive”, TB skin test reaction
• can develop active TB disease if they do not receive treatment for latent TB infection

Some people who have latent TB infection never develop active TB disease. In these individuals, the TB bacteria remain inactive for a lifetime without causing disease. However, in other persons, especially those who have weak immune systems, like with AIDS or cancer, the bacteria become active and cause TB disease.

What is active TB disease?

TB bacteria become active if the immune system can not stop them from growing. The active bacteria begin to multiply in the body and cause active TB disease. The bacteria attack the body and destroy tissue. If this occurs in the lungs, the bacteria can actually create a hole in the lung. Some people develop active TB disease soon after becoming infected, before their immune system can fight the TB bacteria. Other people may get sick later, when their immune system becomes weak for another reason.

Babies and young children often have weak immune systems. People infected with HIV, the virus that causes AIDS, also have very weak immune systems. Other people can have weak immune systems too, especially those with any of the following conditions:

• substance abuse (drugs or alcohol)
• diabetes mellitus
• cancer
• leukaemia or Hodgkin's disease
• severe kidney disease
• low body weight
• certain medical treatments (such as corticosteroid treatment or organ transplants)
• specialized treatment for rheumatoid arthritis or Crohn’s disease

Symptoms of TB depend on where in the body the TB bacteria are growing. TB bacteria usually grow in the lungs. TB in the lungs may cause symptoms such as

• 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 active TB disease are:

• weakness or fatigue
• weight loss
• no appetite
• chills
• fever
• sweating at night

The Difference between Latent TB Infection and Active TB Disease

Should I get tested for TB?

You should get tested for TB if:

• You have spent time with a person known to have active TB disease or suspected to have active TB disease.
• You have HIV infection or another condition that puts you at high risk for active TB disease.
• You think you might have active TB disease.
• You inject illegal drugs.