PARIS - Researchers on Thursday sounded the alarm over drug-resistant tuberculosis, calling it a curse that was swiftly becoming more difficult and costly to treat.
In eight countries they studied, 43.7 percent of TB patients did not respond to at least one second-line TB drug, a strategy used when the most powerful first-line drugs fail.
The probe, covering Estonia, Latvia, Peru, the Philippines, Russia, South Africa, South Korea and Thailand, is reported in The Lancet medical journal.
"Most international recommendations for TB control have been developed for MDR (multidrug-resistant) TB prevalence of up to around five percent. Yet now we face prevalence up to 10 times higher in some places," Sven Hoffner of the Swedish Institute for Communicable Disease Control wrote in a comment carried by The Lancet.
The study also found a 6.7 percent rate for an even more worrying form of resistance called XDR -- for extensively drug-resistant - TB. It means a patient who does not respond to any two second-line drugs.
An airborne disease of the lungs, tuberculosis is usually treatable with a six-month course of antibiotics.
But if patients do not take their medicines as prescribed, the bacteria that causes TB can develop resistance to the drugs. In rare cases, people can also be infected with already resistant strains.
MDR TB in the United States can cost as much as $250,000 (200,000 euros) per patient to treat.
XDR TB requires about two years of treatment with even more expensive drugs that often cause side-effects and offer no guarantee of a cure.
According to the World Health Organisation (WHO), 8.8 million people fell ill with TB in 2010 and 1.4 million died. Co-infection with the disease causes about a quarter of all deaths among people with HIV.
"So far, XDR TB has been reported in 77 countries worldwide, but exact prevalence remains unclear," study author Tracy Dalton of the US Centers for Disease Control and Prevention (CDC) said.
XDR TB prevalence in the countries measured ranged from 0.8 percent in the Philippines to 11.3 percent in Russia and 15.2 percent in South Korea.
Further research is needed "since the true scale of the burden of MDR and XDR tuberculosis might be underestimated and seems to be rapidly increasing," said Hoffner.