Tuberculosis is a respiratory disease caused by the Mycobacterium tuberculosis bacterium. The bacteria is capable of infecting any area of the human body, but most cases occur in the lungs.

Transmission occurs through the air, when a person inhales the breath of someone infected with the bacteria. As a result, tuberculosis can easily spread, although it is most likely to be transmitted to people the victim spends a lot of time with on a daily basis. Once the bacteria finds its way into the lungs and multiplies, it can pass into the blood stream and reach other areas of the body.

Most people who inhale the bacteria will develop a latent infection, in which they show no symptoms and aren't contagious, yet carry the bacteria. A latent infection can transform into a full blown tuberculosis infection at random, but does not always do so. A latent infection occurs when the body's immune system is able to stop the bacteria from multiplying fast enough to cause a severe infection.

Once tuberculosis infects the lungs, it begins to destroy the tissue. This process usually causes severe coughing, difficulty breathing, chest pain, and fluid buildup in the lungs. If tuberculosis is left untreated, it can result in death.

In earlier times, tuberculosis was the leading cause of death in the United States. Victims first recognized that they had it after coughing up spots of blood into their handkerchief. Tuberculosis medication was first developed in the 1940s, causing a sharp decrease in the number of infections. In 2000, 16,000 tuberculosis cases were reported, which is lower than some other bacterial infections, but still rather high.

Many famous people have been impacted by this disease or even died from it. Edgar Allan Poe, for example, watched as most of the people close to him died from the terrible disease. John Henry "Doc" Holliday became a notorious outlaw after finding out that he was infected.