Tuberculosis is not caused by a virus. Instead, it is caused by a bacteria called Mycobacterium tuberculosis (M. tuberculosis). The bacteria typically affects the lungs, making it more contagious, but can also attack other parts of the body.
Tuberculosis bacteria is most often spread person to person. It is released into the air when someone with the active tuberculosis coughs or sneezes. The bacteria spread easily like the cold or flu, especially in crowded places with poor airflow. The longer you breathe these germs, the more likely you are to become infected.
However, tuberculosis cannot survive outside the body. So it cannot be spread by shaking hands, sharing food or drink, or touching surfaces that an infected person has touched.