Tuberculosis Tuberculosis (TB) is caused by bacteria (Mycobacterium tuberculosis) that most commonly affects the lungs but can involve other organs as well. Patients, suffering from pulmonary TB, can spread the bacilli by coughing, sneezing and spitting. When a person develops active TB disease, the symptoms (such as cough, fever, night sweats, or weight loss) may be mild for many months, which can lead to delay in seeking care, and results in transmission of the bacteria to others. Active, drug-susceptible TB disease is generally treated with a standard 6-month course.