Tuberculosis is caused by the Mycobacterium tuberculosis bacteria. The disease usually affects the lungs but it can also affect any organ of the body like the bones or heart. Earlier, before the discovery of antibiotics, the disease was more popularly known as consumption as there was no treatment and people suffering from the disease would just waste away and die. However, today there are many antibiotics available to treat people and most recover without any problems.
So, how does a person get tuberculosis? The bacteria that are responsible for the disease are released into the air when an infected person coughs, sneezes, spits or shouts. These airborne bacteria are then inhaled by uninfected people who are close by or in the vicinity. On inhalation of the bacteria, the disease sets in after an incubation period, which can last as long as few years. A person cannot get the disease by touching or shaking hands with an infected person. The only way to get the disease is to breathe the air when you are close to the infected person; and inhaling a small number of bacteria can cause the disease.
There is one form of the disease which a person can get by drinking unpasteurized milk. This form of the disease is caused by Mycobacterium bovis bacteria. Earlier, this was the main cause of the disease among children but now it rarely occurs because most milk is pasteurized.
If a person suffering from tuberculosis does seek medical help and treatment, he is bound to infect 10 to 15 people each year. However, it is not necessary that a person infected with the Mycobacterium will fall sick with the disease.