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Drug-resistant TB rising in Russia, Philippines, India, S. Africa

May 13, 2017

Cases of multidrug-resistant and extensively drug-resistant tuberculosis are expected to increase in four countries with a high burden of multidrug-resistant tuberculosis from 2000 to 2040, reported researchers.

According to findings from a compartmental model, the percentage of multidrug-resistant tuberculosis among incident cases of tuberculosis will increase to 12.4% (95% prediction interval 9.4 to 16.2) in India, 8.9% (4.5 to 11.7) in the Philippines, 32.5% (27.0 to 35.8) in Russia, and 5.7% (3.0 to 7.6) in South Africa in 2040, reported Aditya Sharma, MD, of the U.S. Centers for Disease Control and Prevention, and colleagues.

Similarly, the percentage of incident extensively drug-resistant TB was estimated to increase for all countries — reaching 8.9% (95% prediction interval 5.1 to 12.9) in India, 9.0% (4.0 to 14.7) in the Philippines, 9.0% (4.8 to 14.2) in Russia, and 8.5% (2.5 to 14.7) in South Africa in 2040, they wrote in The Lancet Infectious Diseases.

While multidrug-resistant tuberculosis is resistant to more than one of the first-line drugs for the disease, extensively drug-resistant tuberculosis is additionally resistant to fluoroquinolones and at least one of the second-line injectable tuberculosis drugs, noted the researchers.

“This study uses a complex model bringing together the best available data from multiple sources in four countries hit hard by the drug-resistant tuberculosis epidemic,” wrote Sharma.

“Our findings show that cases in these countries are expected to rise over the next two decades, and that fewer cases over time will be caused by acquired drug resistance during tuberculosis treatment. Person-to-person transmission will become the engine that drives drug-resistant tuberculosis in these countries,” he continued.

The researchers created a mathematical model to forecast how tuberculosis is likely to progress in the four most-affected countries between 2000 and 2040. They used data from the World Health Organization, as well as surveys which estimated the number of drug-resistant tuberculosis cases, in order to predict how many cases of multidrug-resistant and extensively drug-resistant tuberculosis would develop during the 40-year period.

The model simulated transfer between six main states of tuberculosis: uninfected or susceptible; latent tuberculosis infection; active tuberculosis disease; active tuberculosis disease that had been detected and patient was receiving the correct treatment on the basis of the underlying drug resistance (i.e., non-MDR tuberculosis versus MDR tuberculosis); tuberculosis disease that had been successfully treated; and tuberculosis disease that spontaneously resolved without treatment.

Sharma and colleagues found that fewer cases of drug-resistant tuberculosis will be caused by strains acquiring resistance – falling from around 30% of cases of multidrug-resistant tuberculosis in 2000 to 20%-25% in 2040.

While acquired drug resistance caused 80% of incident extensively drug-resistant tuberculosis in 2000, this estimate would decrease to less than 50% by 2040, they added.

Instead, infections with drug-resistant tuberculosis will increasingly come from person-to-person transmission of already resistant strains, rather than non-resistant strains acquiring resistance.

Sharma and colleagues called for additional control efforts to stop the spread of multidrug-resistant and extensively drug-resistant tuberculosis in countries with a high burden of multidrug-resistant tuberculosis.

“We cannot focus solely on curing people with tuberculosis or drug-resistant tuberculosis if we want to halt the epidemic. Even if we prevent new drug-resistant infections, there are enough current cases to keep the epidemic going, and drug-resistant tuberculosis will continue to be an increasingly dangerous threat so long as resistant strains spread through the air from one person to another,” noted Sharma.

Instead, he suggested strengthening infection control measures, focusing on households, health centers, and communities to prevent tuberculosis spreading from person to person, and developing more effective diagnostic tests to rapidly and accurately detect drug resistance.

Writing in an accompanying editorial, Andrei Mariandyshev, MD, of Northern State Medical University in Russia, commented that the most important measure in preventing the spread of multidrug-resistant tuberculosis is the implementation of short-course regimens of chemotherapy for patients.

“Introduction of 9-12 month courses of multidrug-resistant tuberculosis therapy will increase the effectiveness of treatment and reduce the total number of anti-tuberculosis drugs during the course of treatment and save funds that can be used to treat more patients,” wrote Mariandyshev.

He added that the use of new drugs will improve the quality of treatment for adults and children with drug-resistant tuberculosis and will help to eliminate tuberculosis globally.

Study limitations included the use of regional data for Russia and India which may not represent the true national disease burden. Additionally, the model didn’t account for population density and migration which could increase the transmission rates.

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