GENEVA - Extremely drug-resistant strains of tuberculosis could spark a "practically uncontrollable" epidemic among HIV/AIDS sufferers in areas like Africa, a World Health Organisation (WHO) official said on Tuesday.

Mario Raviglione, director of the United Nations agency's Stop TB Department, said health experts needed to ensure a recently discovered strain -- known as XDR-TB -- did not trigger a wave of infections among those with weak immune systems.

He said better diagnostic tools and improved health care procedures -- including isolation rooms for those afflicted with the highly contagious bug -- were vital to stop its spread.

"If all the elements of good TB control are put in place, we have a chance of taking care of this disease," the Italian doctor said in an interview at the WHO's headquarters.

"If we let the situation ... with XDR go out of control, as it might well do, then we are in trouble. All of our gains over the last 10 years in controlling TB would be lost."

Tuberculosis, an airborne disease spread like the common cold, afflicts about 9 million people each year and kills 1.6 million. It is normally treatable with antibiotics but drug-resistant strains have emerged in past years, complicating a U.N.-backed drive to stop the spread of the disease by 2015.

More than 400,000 people were found in 2004 to have developed "multi-drug resistant" strains that could not be treated with at least two key first-line tuberculosis drugs, with most cases in China, India and Russia.

XDR-TB, a "super bug" which resists three or more classes of second-line tuberculosis drugs, has been identified in 28 countries worldwide, with cases concentrated in the United States, Latvia and South Korea.

In South Africa, the XDR strain has killed nearly 200 people since September, mainly HIV patients unable to fend it off.

Raviglione said the strain could cause widespread deaths among those with HIV/AIDS, given their susceptibility to tuberculosis and the difficulty in treating it.

"Either we intervene rapidly to stop the spread of this strain, or you could foresee in the future that this strain would replace the other one," he said. "That would make it practically uncontrollable."

New antibiotics and drugs to fight XDR-TB could take more than five years to reach the market, Raviglione said, so countries needed to boost their laboratory capacities to quickly identify which patients have drug-resistant TB strains.

"In South Africa they are capable, that is why they discovered it. But we don't know what's happening in Mozambique, in Lesotho, in Swaziland, in Zimbabwe," he said, noting it was possible the strain was more widespread in the region.

Africa accounted for most of the world's tuberculosis deaths in 2004, followed by southeast Asia, according to WHO data.