Similar to the common cold, tuberculosis (TB) is spread through the air. When people are sick with pulmonary TB, they can infect other people through coughing, sneezing, talking or spitting. A healthy person needs only to inhale a small number of TB germs to become infected. Left untreated, each person with active TB will infect an average of 10-to-15 people per year.

People infected with TB will not necessarily contract the disease. The immune system “walls off” the TB germs, called bacilli, which can lie dormant for years. When the body’s immune system becomes weakened, the risk of contracting the disease is increased.

Some facts about TB:

• Nearly 1 percent of the world's population becomes infected with TB each year.
• One-third of the world's population is infected with the TB bacillus.
• According to the World Health Organization, 2 million people die each year from TB.

The most common anti-TB drugs are:

• Isoniazid;
• Rifampicin;
• Pyrazinamide;
• Streptomycin;
• Ethambutol.

Unfortunately, single-drug, treatment-resistant bacilli strains have been documented in every country surveyed. More recently, multidrug-resistant (MDR) and extensive drug-resistant (XDR) strains, which are particularly dangerous, have emerged. MDR-TB is defined as TB bacilli resistant to at least isoniazid and rifampicin, which are considered to be the two most powerful anti-TB drugs. XDR-TB is defined as TB bacilli resistant to isoniazid and rifampin, as well as at least two of the six primary classes of second-line anti-TB drugs.

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