TB presently causes about 1.7 million deaths a year worldwide, but researchers are worried about the emergence of strains that are resistant to drugs.

Drug resistance is caused by poor TB control, through taking the wrong types of drugs for the incorrect duration.

Multi-drug resistant TB (MDR TB), which describes strains of TB that are resistant to at least two of the main first-line TB drugs, is already a growing concern.

Globally, the WHO estimates there are about 425,000 cases of MDR TB a year, mostly occurring in the former Soviet Union, China and India.