An estimated 480,000 people contract MDR-TB each year, accounting for roughly five per cent of the 9.6 million TB cases recorded annually worldwide.
Unlike simple tuberculosis, MDR-TB has proved extremely difficult to treat, requiring patients to take painful injections and thousands of pills over a period of 18-24 months, often with devastating side effects, including deafness in some cases.
The old MDR-TB treatment regimen "is pretty much a tragedy," said Mario Raviglione, the head of WHO's TB programme, noting the 50 per cent success rate.
But it does not include newly-discovered drugs. Instead, it is made up of a cocktail of existing medication, including one repurposed drug originally used to treat leprosy.
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The treatment process is also cheaper, possibly costing as little as USD 400 (350 euros) per patient, compared to the USD 1,500-USD 3,000 under the old regimen, Raviglione told reporters.
"This is a critical step forward," he said.
Roughly 30 per cent of MDR-TB patients infected with an especially complicated form of the disease will not be able to benefit from the new treatment regimen, because of added drug resistance.
TB is a bacterial disease that mostly infects the lungs and kills an estimated 1.5 million people per year, mostly in low and middle income countries.
An estimated 190,000 people die from MDR-TB every year.
Despite the threat, there has been little investment and research aimed at improving treatment, said I.D. Rusen, vice president of the Union against Tuberculosis and Lung Disease, which helped develop the new regimen.