The Lancet just published an important new study showing the prevalence of Tuberculosis in China has been reduced by half since 1990, from about 170 cases per 100,000 people to 59 cases per 100,000 in 2010. This is hugely significant to the people of China and the world. It is also proof positive that a World Health Organization guideline for treating TB can be highly effective. Treating TB generally requires a patient to take medicine once a day for several months. In the 1990s the World Health Organization developed the Directly Observed Short Course Treatment (DOTS) guidelines for countries with high TB burdens. DOTS requires that a health worker or trusted individual physically observe the patient take her dose of TB medicine. The idea is that the patient will be less inclined to stop taking her medicine once her symptoms disappear, but before the TB is gone from her system. (If treatment is interrupted, the TB can re-appear, or, worse, the TB can develop resistance to the treatment–and much more expensive second line drugs would be required.) The medicine to treat first line TB is not expensive. But the infrastructure to implement DOTS can be costly. After all, to maximize impact, you want the treatment options to be as convenient as possible for patients. Authorities in China — to their credit — decided to invest in a DOTS strategy for their provinces with their highest burden of TB in the 1990s, then expanded to the entire country in 2005. The Lancet review offers evidence that this strategy worked. It also shows that other countries with similarly high burden can sharply reduce TB incidence by implementing the World Health Organization’s guidelines.