TB is transmitted from person to person, usually by inhaling bacteria-carrying air droplets. When a person sick with TB coughs, sneezes, or speaks, small particles that carry two to three bacteria surrounded by a layer of moisture are released in the air. When another person inhales these particles, the bacteria may lodge in that person’s lungs and multiply. (TRANSMISSION AND INFECTION, Stages Tuberculosis Disease, TB Inhaling Bacteria-Carrying)
A less common route of transmission is through the skin. Pathologists and laboratory technicians who handle TB specimens may contract the disease through skin wounds. TB has also been reported in people who have received tattoos and people who have been circumcised with unsterilized instruments. (TRANSMISSION AND INFECTION, Stages Tuberculosis Disease, TB Inhaling Bacteria-Carrying)
A person may become infected with TB bacteria and not develop the disease. His or her immune system may destroy the bacteria completely. In fact, only 5 to 10 percent of those infected with TB actually become sick. If a person does contract the infection, disease can develop in two stages: primary and secondary. (TRANSMISSION AND INFECTION, Stages Tuberculosis Disease, TB Inhaling Bacteria-Carrying)