Tuberculosis, a bacterial infection, most commonly affects the lungs. Tuberculosis can also affect the central nervous system, lymphatic system, circulatory system, genitourinary system, bones and joints. Often Called TB for short, tuberculosis is the most common major infectious disease today. With that title the virus is infecting two billion people which is approximately one-third of the world's population. Nine million new cases of active disease annually, resulting in two million deaths. Most of these cases and deaths are in developing countries. Ninenty percent of those that are infected have asymptomatic latent TB infection (LTBI). This is alot of numbers: There is a ten percent chance that in the lifetime of LTBI that it will progress to active TB disease. This active disease if left untreated, will kill more than fifty percent of its victims. All of these numbers make tuberculosis one of the top three infectious killing diseases in the world. HIV/AIDS kills 3 million people each year, TB kills 2 million, and malaria kills 1 million. Tuberculosis is caused by a slow-growing aerobic bacterium that divides every 16 to 20 hours. This division is extremely slow when compared to other bacteria, which tend to have division times that are measured in minutes. In many patients the infection of Tuberculosis waxes and wanes. Treatment with appropriate antibiotics kills bacteria and allows healing to take place. Areas where Tuberculosis has affected will eventually be replaced by scar tissue. A complete medical evaluation for Tuberculosis includes a medical history, a physical examination, a tuberculin skin test, a serological test, a chest X-ray, and microbiologic smears and cultures. This is quite an extensive procedure as you can see, but if you look at the numbers above it is a necessary process.