Tuberculosis (TB) is a bacterial infection caused by bacilli known as Mycobacterium tuberculosis. TB often affects the lungs, but may damage other parts of the body.

According to the Center for Disease Control and Prevention (CDC), TB is transmitted through the air when someone with TB of the lungs or throat coughs, sneezes or talks. Symptoms of TB include: a persistent bad cough, coughing up blood, weakness, fever and chills, night sweats and weight loss. The World Health Organization (WHO) reports that people who are infected with TB do not necessarily become immediately sick or symptomatic since the body "walls off" the bacilli. Dormant TB often emerges as an illness later in life when a person's immune system is weakened. Treatment for TB usually requires a six month course of antibiotics. Untreated TB can be fatal.

WHO estimates that each person with untreated active TB will infect on average 10-15 other people each year and one-third of the world's population is currently infected. WHO reports that in 2005, 1.6 million people died from TB.

Although medications have been developed in the last 50 years to treat TB, strains of drug-resistant TB have been emerging. WHO reports that the presence of Extensively Drug-Resistant (XDR) TB, especially among HIV patients, is a "serious threat to TB control, and confirms the urgent need to strengthen basic TB control." ( See theĀ WHO Fact Sheet on Tuberculosis)