How to Stop the Fast March of Drug-Resistant Tuberculosis
Public health professionals have warned about drug-resistant tuberculosis for years. Now comes news out of India and China to feed the concern.
Doctors in India have documented more than a dozen cases of TB so tenacious, it responds to no known drug. This is a scary proposition in a country where 2 million of the world’s 9 million annual TB cases occur and where malnutrition, overcrowding and a weak health system create a hotbed for the often-fatal disease.
Conventional drug resistance is also turning out to be a problem in China, which has a million TB cases a year. In a study published this month in the New England Journal of Medicine, 1 of 10 TB patients there had multidrug resistance, and 1 in 120 had extensive drug resistance.
Previously, resistance was thought to exist mainly in patients who’d had regular TB and didn’t complete the required six months of treatment or didn’t get sufficiently strong drugs, enabling the bacteria to develop resistance. But in the China study, most cases were in new patients. This means that resilient bacteria are being passed from person to person.
This calls for a new approach to TB in the developing world. In wealthy countries, people who are suspected of having TB are immediately tested for drug-resistant strains. In poor ones, that test is done, at best, only after patients fail to recover on first-line medications, which provide them no benefit and only teach more bacteria to become elusive.
Screening all TB cases for resistance is an enormous challenge. The most common method for testing TB in the developing world is to examine sputum smears under a microscope; this misses about half of all cases and provides no information on resistance. Culture-based resistance tests take weeks to produce results. And conventional rapid tests that recognize the DNA of TB bacteria require sophisticated labs that are rare outside of developed countries.
However, a recent innovation makes mass screening feasible. A breakthrough test, which detects resistance to the popular TB drug rifampicin -- a strong indicator of multidrug resistance -- provides results in two hours and can be conducted without an advanced lab. Called Xpert MTB/RIF, it was designed by California-based Cephied Inc. in collaboration with the nonprofit Foundation for Innovative Diagnostics with funding from the Bill and Melinda Gates Foundation.
In mid-June, Unitaid, a global health organization housed at the World Health Organization and financed mainly by airline ticket taxes, and the Stop TB Partnership, a public-private umbrella group also housed at the WHO, allocated $40 million to deploy the test in 20 countries. This is an important step to making it universally available.
Ideally, TB patients found to have mutant strains would then receive the right treatment. Because advanced regimens can cost 50 to 200 times the $20 it typically costs to treat ordinary TB, a significant investment by donors and governments in affected countries is needed. The Stop TB Partnership estimates it will take $7.1 billion to monitor, diagnose and treat drug-resistant TB in the developing world. As relatively prosperous countries, India and China, which fund just 59 percent and 67 percent of their TB budgets respectively, should become self-sufficient and, with other emerging economies, contribute to the global effort.
Controlling drug-resistant TB is expensive, but so is inaction. TB spreads easily through the air when an infected person coughs, sneezes or even speaks. It respects no borders, particularly in a world of increasing international travel. All three Indian cities where the untreatable strain has been identified -- New Delhi, Mumbai and Bangalore -- are popular business destinations. The last time the U.S. faced a serious outbreak of multidrug-resistant TB, in the late 1980s, New York City alone spent more than $1 billion controlling it. Attacking drug-resistant TB is not so much a cost as an investment.
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