In a large international study published in the Lancet medical journal on Thursday, scientists have found an alarming number of cases of the lung disease tuberculosis in Africa, Asia, Europe and Latin America that are resistant to up to four powerful antibiotic drugs.

Commenting on the study Sven Hoffner of the Swedish Institute for Communicable Disease Control, said, "Most international recommendations for TB control have been developed for MDR-TB prevalence of up to around 5 percent. Yet now we face prevalence up to 10 times higher in some places, where almost half of the patients ... are transmitting MDR strains." MDR-TB is resistant to at least two first-line drugs - isoniazid and rifampicin - while XDR-TB is resistant to those two drugs as well as a powerful antibiotic type called a fluoroquinolone and a second-line injectable antibiotic.

TB is already a worldwide pandemic that infected 8.8 million people and killed 1.4 million in 2010. Drug-resistant TB is more difficult and costly than normal TB to treat, and is more often fatal. Treating even normal TB is a long process, with patients needing to take a concoction of powerful antibiotics for six months.