Tuberculosis (TB) is a contagious infection caused by bacteria called Mycobacterium tuberculosis. It primarily affects the lungs but can also involve other parts of the body, such as the kidneys, spine, and brain. TB spreads through the air when a person with active TB disease coughs or sneezes, releasing bacteria into the air. A small amount of TB protein (antigen) is injected under the skin. A raised bump (induration) at the site within 48-72 hours indicates a positive result, suggesting TB infection.
