The fear is that a fast-spreading, anti-biotic resistant strain will spread via mutation or bioterrorism.

The World Health Organization (WHO) estimates that two billion people — one third of the world’s population — are infected with Mycobacterium tuberculosis.

25 January 2014. TB kills 1.4 million people a year. TB increasingly resists the few antibiotics still working, and 9% resist almost all drugs,  There are 600,000 cases around the world that resist several drugs. These cases have risen 65% since 2006.  In South Africa the drug to treat the most resistant TB failed 90% of the time, so it continues to spread.

22 October 2014. Improved data reveals higher global burden of tuberculosis. World Health Organization. The multidrug-resistant TB (MDR-TB) crisis continues, with an estimated 480,000 new cases in 2013. Worldwide, about 3.5% of all people who developed TB in 2013 had this form of the disease, which is much harder to treat and has significantly poorer cure rates. While the estimated percentage of new TB cases that have MDR-TB globally remains unchanged, there are severe epidemics in some regions, particularly in Eastern Europe and Central Asia. In many settings around the world, the treatment success rate is alarmingly low. Furthermore, extensively drug-resistant TB (XDR-TB), which is even more expensive and difficult to treat than MDR-TB, has now been reported in 100 countries.

Wilson, C. 21 January 2015. Soviet Union fall helped drug-resistant TB to take off. NewScientist.