BEIJING, April 1 (Xinhua) -- The World Health Organization (WHO) urged countries where tuberculosis (TB) is prevalent to take urgent action to curb the spread of multidrug-resistant and extensively drug-resistant (M/XDR-TB) forms of the disease.

    Addressing a meeting here Wednesday, WHO Director-General Margaret Chan said the world faced a "precarious situation" due to the emergence and spread of drug-resistant TB.

    "The situation is already alarming, and it is poised to grow much worse, very quickly," she told health ministers and officials from more than 30 countries and regions, who gathered at the Ministerial Meeting of High M/XDR-TB Burden Countries, organized by WHO.

    Although TB is preventable and treatable, when the TB bacillus becomes resistant to the two most powerful first-line anti-TB drugs, the disease develops into the multidrug-resistant TB (MDR-TB).

    The more serious XDR-TB, a sub-strain of MDR-TB that developed from the highly drug-resistant strains, has been reported in more than 50 countries -- mainly in Asia, Africa and Europe, according to the WHO.

    Chan said WHO reports on drug-resistant TB had documented the highest levels of multidrug resistance ever recorded in the general population.

    The organization estimated that more than 500,000 new cases of MDR-TB occurred during 2007.

    "If MDR-TB is not vigorously addressed, it stands to replace the mainly drug-susceptible strains currently responsible for 95 percent of the world's TB cases," she said.

    About 1.7 million people die from TB annually, according to the WHO, which blamed improper use of drugs and mismanagement of treatment for causing multi-drug resistance.

    Chan urged that high priority be given to the epidemic "because national TB programs cannot, by themselves, manage these new threats."

    She said the cost of treating MDR-TB can be as much as 200 times higher than normal TB.

    As a result of the global economic downturn, "we need to look very carefully at areas of public health where any lapse in current efforts will bring us much a bigger and heavier bill very soon.

    "TB control is a prime example," she said.