TB is spread through the air from one person to another. The bacteria are put into the air when a person with TB disease of the lungs coughs, sneezes or talks. 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 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 spread to other people. TB in other parts of the body, such as the kidney or spine, is usually not infectious.

People with TB disease are likely to spread TB to people who come in close contact and spend time with them everyday. This includes family members, friends, and coworkers.