Tuberculosis is caused by a bacterium called Mycobacterium tuberculosis. People with active TB disease in the lungs or voice box can spread the disease. They release tiny droplets that carry the bacteria through the air. This can happen when they're speaking, singing, laughing, coughing or sneezing. A person can get an infection after inhaling the droplets. The disease is more likely to spread when people spend a lot of time together in an indoor space. So the disease spreads easily in places where people live or work together for long periods. Also, the disease spreads more easily in crowded gatherings. A person with a latent TB infection cannot pass the disease to other people. A person taking drugs to treat active TB disease usually can't pass the disease after 2 to 3 weeks of treatment.