Multi-Drug-Resistant Tuberculosis Epidemic May Be Larger Than Previously Thought

The epidemic of multidrug-resistant (MDR) tuberculosis (TB) may be larger than previously suspected, according to an Article in The Lancet. The study found anti-TB drug resistance in virtually all of the 79 countries surveyed, with particularly high levels in areas of the former Soviet Union and some provinces of China.

About a third of the world’s population is infected with Mycobacterium tuberculosis, 8.9 million people develop the disease annually, and in 2004, 1.7 million deaths occurred. The emergence of drug-resistant strains occurs with the wide misuse of antimicrobials. MDR-TB is defined as resistance to at least the two most potent anti-TB drugs, isoniazid and rifampicin. In 1994, the Global Project on Anti-Tuberculosis Drug Resistance Surveillance was set up to determine the prevalence, patterns, and trends of anti-TB drug resistance around the world.

Mario Raviglione (World Health Organization) and colleagues analysed data on susceptibility to four anti-TB drugs, gathered in the third round of the Global Project from surveys or ongoing surveillance in 79 countries. The researchers estimate that 424 000 cases of MDR-TB emerged worldwide in 2004. Three countries - China, India, and Russia - account for over half of these cases. The median prevalence of MDR-TB in new cases was 1%. Eight countries, including Kazakhstan and Latvia, reported prevalence of multidrug resistance above 6.5%. A worrying increase in the prevalence of resistance to any drug, including MDR-TB was found in Botswana and Tomsk Oblast in Russia. The investigators found decreasing trends in multidrug resistance in the USA, Hong Kong, and Cuba.

Dr Raviglione concludes: “MDR-TB is a precursor to XDR-TB, recently reported among HIV-infected people in South Africa. The findings of the Global Project emphasise the importance of implementing sound tuberculosis control activities to prevent further creation of MDR tuberculosis and the necessity of mainstreaming high-quality treatment for MDR tuberculosis into routine tuberculosis control programmes. Otherwise XDR-TB is bound to keep emerging as a fatal variant of TB, especially in high HIV prevalence settings.”

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Contact: Joe Santangelo
Lancet