XDR-TB develops when there is severe drug resistance. It responds to very few drugs and it is often difficult to find the drug that can treat XDR-TB. Approximately 480,000 people developed MDR-TB worldwide in 2014. More than half of these cases were in India, the People’s Republic of China and the Russian Federation. Estimates are that about 9.7% of MDR-TB cases had XDR-TB. Treatment success for XDR- TB is only about 20%.