Multi-drug resistant TB may be widespread.

The global epidemic of multi-drug resistant tuberculosis may be larger than thought, according to a recent article in the Lancet.

The study found anti-TB drug resistance in virtually all of the 79 countries surveyed, with particularly high levels in the former Soviet Union and China.

About a third of the world's population is infected with Mycobacterium tuberculosis and 8.9 million people develop the disease each year. In 2004, 1.7 million people died from the disease. The emergence of strains that are resistant to the two most potent anti-TB drugs is linked to wide misuse of antimicrobials, the study noted.

The study, published Dec. 16, estimated 424,000 cases of multi-drug resistant TB emerged worldwide in 2004. China, India and Russia accounted for more than half of those cases. The study's authors found decreasing trends of the disease in the United States, Hong Kong and Cuba.

The researchers noted that despite the work of the Global Project on Anti-Tuberculosis Drug Resistance Surveillance, which was established in 1994, "there remain important gaps in data from many countries with the highest burden of tuberculosis, areas where the HIV epidemic is fueling the tuberculosis epidemic, and countries where prevalence of drug resistance is expected to be high because of historically poor tuberculosis control." The authors also noted that one of the main obstacles to expanded surveillance is the lack of functioning laboratory networks.