TB is a leading infectious killer on the international landscape, and poorly designed disease control systems exacerbate the problem by leading to the formation of drug-resistant strains of the microbe. Moreover, comprehensive data on global trends in drug resistance is lacking, which makes it difficult to control the overall situation.

To increase the body of information, a dozen physicians oversaw a survey, extending on previous WHO endeavors, of 58 international sites between 1996 and 1999. They set out to determine single- and multidrug resistance levels among new and previously treated cases. The researchers found that Estonia, Latvia, and Russia continue to have a serious problem, and they uncovered areas newly identified as having a high prevalence of multidrug resistance, such as parts of China and Iran.

For patients who were newly diagnosed, the frequency of resistance to at least one of the “first-line” TB drugs—isoniazid, rifampin, streptomycin, or ethambutol—ranged from 1.7% in Uruguay to 36.9% in Estonia. In Estonia, the number of newly diagnosed resistant cases increased from 28.2% in 1994 to 36.9% in 1998. In Denmark, such cases increased from 9.9% in 1995 to 13.1% in 1998.

Whereas the median number of newly diagnosed multidrug-resistant cases was only 1.0%, the prevalence was much higher in Estonia (14.1%); the Henan Province in China (10.8%); Latvia (9.0%); the Russian oblasts of Ivanovo (9.0%) and Tomsk (6.5%); Iran (5.0%); and the Zhejiang Province in China (4.5%). In Estonia, clearly one of the biggest problem areas, the number of all multi drug-resistant cases, previously treated and newly diagnosed, increased from 11.1% in 1994 to 18.1% four years later. In France and the United States, meanwhile, the total number of cases decreased significantly.

The study’s authors recommended the greater use of proven strategies for intervention, such as the WHO directly observed treatment short-course strategy, which emphasizes government commitment; effective diagnosis; continual, carefully monitored treatment; and accurate record keeping. The physicians stressed that “second-line” drugs should be used only as part of well- structured programs of tuberculosis control; otherwise, resistant strains will continue to develop.