Mycobacterial diseases are infections caused by bacteria from the Mycobacterium genus, which includes species like Mycobacterium tuberculosis and Mycobacterium leprae. These bacteria can lead to serious health issues, with tuberculosis (TB) primarily affecting the lungs and leprosy (Hansen's disease) impacting the skin and nerves. Transmission of mycobacterial diseases often occurs through the air, especially in the case of TB, when an infected person coughs or sneezes. Diagnosis typically involves skin tests, blood tests, or imaging studies, and treatment usually requires a long course of antibiotics to effectively eliminate the bacteria.