Tuberculosis (TB) is a contagious bacterial disease that primarily involves the lungs. Like the common cold, it spreads through the air. Only people who are sick with TB in their lungs are infectious. When infectious people cough, sneeze, talk or spit, they propel TB germs, known as bacilli, into the air. A person needs only to inhale a small number of these to be infected. TB can also affect other parts of the body, such as the brain, the kidneys or the spine.

Unlike bugs that kill almost every person they infect, Mycobacterium tuberculosis (M. TB) infects many individuals yet causes disease in relatively few. After gaining entry into a person's lungs, the bacteria frequently live unobtrusively for years or decades. During this latent infection, the person generally suffers no obvious disease symptoms and cannot pass on the germ to others. Again, individuals that have TB infection cannot spread the disease and people with TB infection can be treated to prevent infection from developing into TB disease.

However, if the immune system weakens—whether from age, poor nutrition or other diseases—the bacteria can emerge from their hiding places and cause full-blown TB. Various factors that weaken the immune system, such as multiple medical problems, chemotherapy, HIV Infection, or any other immuno-suppressive conditions may trigger or contribute to reactivation of the infection.

Left untreated, each person with active TB disease will infect on average between 10 – 15 people every year. People with TB disease can be cured if they obtain medical evaluation and appropriate medication. The antimicrobials that kill TB germs are specific for tuberculosis.

Cavitatory Pulmonary TB