Tuberculosis (TB) is caused by bacteria Mycobacterium Tuberculosis that most often affect the lungs. Tuberculosis is curable and preventable. It is spread from person to person through the air. When people with lung TB cough, sneeze or spit, they propel the TB germs into the air. A person needs to inhale only a few of these germs to become infected.

About one-third of the world's population has latent TB, which means people have been infected by TB bacteria but are not (yet) ill with disease and cannot transmit the disease.

TB in the lungs or throat (pulmonary TB) are the only forms of the illness that are infectious, which means it can be passed on to other people. However, TB can also affect any other part of the body including kidneys, brain or bones. This is called non-pulmonary TB — and these are not infectious.

When someone with TB in their lungs or throat coughs or sneezes, they send droplets into the air that contain the TB bacteria. If you breathe in these bacteria over a long time you may become ill with TB. But most people will not get ill because:

♦  you normally need to spend many hours close to a person with infectious TB to breathe in enough bacteria to be at risk

♦  most people's immune systems are strong enough to kill off TB bacteria

TB cannot be spread through touch, sharing cutlery, bedding or clothes

People infected with TB bacteria have a lifetime risk of falling ill with TB of 10%. However, persons with compromised immune systems, such as people living with HIV, malnutrition or diabetes, or people who use tobacco, have a much higher risk of falling ill.