Breaking the drug-resistant TB transmission cycle important


Nearly two months after the Health Ministry set a highly ambitious target of working towards elimination of tuberculosis by 2025, a study published in The Lancet Infectious Diseases indicates that India’s TB crisis is all set to snowball by 2040 when one in 10 cases could be drug-resistant. What is even more alarming is that the increased number of drug-resistant cases — both multidrug-resistant TB (resistant to more than one of the first-line drugs) and extensively drug-resistant TB (additionally resistant to fluoroquinolones and at least one of the second-line injectable drugs) — will come from direct transmission from infected people to others rather than by strains acquiring resistance to TB drugs during treatment due to inappropriate treatment or discontinuation of treatment midway. The study found that “most incident” MDR cases are “not caused” by acquired drug resistance, and that acquired drug resistance will become a “decreasing cause” of drug-resistant TB. The increased availability of drugs to fight drug-sensitive TB has led to the emergence of MDR-TB strains. With increasing number of MDR-TB cases, there has been a shift in the way people get infected with drug-resistant TB — from strains acquiring drug resistance during treatment to direct transmission of MDR-TB strains from an infected person. The same trend is seen in the case of XDR-TB too. As a result, in high MDR-TB burden countries such as India, improved treatment outcomes in people might only reduce and not eliminate drug-resistant TB. Till 2015, only about 93,000 people with MDR-TB have been diagnosed and put on treatment.

The study, based on a mathematical model to forecast how TB is likely to progress in the four most-affected countries (Russia, the Philippines and South Africa, India), suggests that the number of new MDR-TB cases in a year in India will touch 12.4% by 2040, up from 7.9% in 2000. In the case of XDR-TB, the incident cases will rise to 8.9%, up from 0.9% in 2000. In 2015, the four countries accounted for about 40% (more than 230,000) of all drug-resistant TB cases in the world. Besides increasing the number of people who are diagnosed early and successfully treated, India’s TB control programme has come up with enhanced interventions to break the transmission cycle of the bacteria in the community. One of the ways this can be achieved is by carrying out immediate screening of all family members of a patient who has been diagnosed with the disease. Contact screening of family members and preventive treatment of all children below the age of five years who have not developed TB disease are already a part of the Revised National Tuberculosis Control Program (RNTCP) but is rarely done. Another important strategy that has to be adopted is making drug susceptibility testing universal and mandatory. Developing more accurate, cheaper and effective diagnostic tests and improved treatment regimens that are less expensive and of shorter duration will also go a long way in winning the war against the disease.

Published in The Hindu on May 12, 2017


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