Tuberculosis (TB) is caused by a bacterium that spreads through the air from an infectious person to another when they cough, speak or sing. Close contacts of sick people and those with weakened immune systems are most at risk. The bacteria settle in the lungs and throat where they grow, then spread through the blood to other parts of the body. TB doesn’t always cause symptoms if the infected person’s body fights to prevent its growth. This is called latent TB which cannot be transmitted, but the infected person will usually test positive and needs treatment to prevent TB disease which occurs 10% of the time. Transmission can also occur through objects that may be contaminated with bodily fluids