Tuberculosis is caused by the bacteria called Mycobacterium tuberculosis. This bacterium is inhaled in the form of microscopic droplets released in the air that come from a person with tuberculosis. It spreads easily because even when a person with TB disease coughs, sneezes, or talks, these bacteria are put in to air.
Scientists and researchers say that TB affects people of all groups but often affects young adults. It is a highly contagious disease and people with a weaker immune system are mostly at risk.
People with HIV/AIDS and cigarette smokers are also at high risk of infected with TB. Malnutrition is the one other major factor in the developing countries where TB is more common.