Introduction Print section Tuberculosis (TB), chronic or acute bacterial infection that primarily attacks the lungs, but which may also affect the kidneys, bones, lymph nodes, and brain. The disease is caused by Mycobacterium tuberculosis, a rod-shaped bacterium. Symptoms of TB include coughing, chest pain, shortness of breath, loss of appetite, weight loss, fever, chills, and fatigue. Children and people with weakened immune systems are the most susceptible to TB. Half of all untreated TB cases are fatal.In 1993 the World Health Organization (WHO) declared TB to be a global emergency, the first such designation ever made by that organization. According to WHO, one individual becomes infected with TB every second, and every year 8 million people contract the disease. Tuberculosis causes 2 million deaths a year. WHO predicts that between 2000 and 2020, nearly 1 billion people will become infected with the TB bacteria and 35 million people will die from the disease.II. Transmission and Infection Print section 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.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. 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 stage...
