Projected spread of drug-resistant tuberculosis threatens elimination targets

An Indian doctor examines a tuberculosis patient in a government TB hospital. (AP Photo/Rajesh Kumar Singh)

Drug-resistant tuberculosis is projected to spread over the next 20 years in four countries that already have a high burden of the disease: Russia, India, the Philippines and South Africa. The expected rise in cases jeopardizes elimination targets set by the World Health Organization (WHO).

A new study by the U.S. Centers for Disease Control and Prevention published yesterday projected that by 2040, one-third of tuberculosis (TB) cases in Russia will likely be drug-resistant. One in 10 cases in India and the Philippines will be drug-resistant as well, while one in 20 cases will be drug-resistant in South Africa.

These four countries represent a wide range of epidemiological conditions, and nearly 40 percent of all drug-resistant TB already occurs within their borders – more than 230,000 cases in 2015.

However, according to the study, the cases in Russia, India, the Philippines and South Africa will not steadily increase because of strains acquiring resistance to drugs. Instead, it will likely be due to an increase in person-to-person transmission of strains that are already either “multidrug-resistant” – to more than one of the vital first-line drugs – or “extensively drug-resistant” – to fluoroquinolones and at least one of the second-line injectable drugs as well.

“We cannot focus solely on curing people with tuberculosis or drug-resistant tuberculosis if we want to halt the epidemic,” the lead author of the study, Aditya Sharma, said in a press release. “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.”

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According to the study, almost one in 10 cases of multidrug-resistant TB in each of the four countries will likely become extensively drug resistant by 2040, compared with around 1 percent in 2000. Therefore, preventing the spread of drug-resistant strains is a critical component to the WHO’s strategy to eliminate “the world’s top infectious disease killer.”

According to the strategy, by 2035, there should be a 95 percent reduction in tuberculosis deaths compared with 2015 and a 90 percent reduction in the tuberculosis incidence rate (less than 10 cases per 100,000 people). There should also be “no affected families facing catastrophic costs due to tuberculosis.”

Currently there are an estimated 10.4 million new cases of tuberculosis each year, and it killed 1.8 million people in 2015. But the rate of mortality is higher for those with drug-resistant TB. About 40 percent of patients diagnosed with multidrug-resistant TB die from the disease, while extensively drug-resistant tuberculosis kills about 60 percent of its patients.

Meanwhile, person-to-person transmission is just too easy: “When people with lung TB cough, sneeze or spit, they propel the TB germs into the air,” according to the WHO. “A person needs to inhale only a few of these germs to become infected.”

Unfortunately, the heaviest burden of disease also falls on communities that are facing socioeconomic challenges, and more than 95 percent of tuberculosis deaths occur in low- and middle-income countries. In these settings, airborne infection control, especially in hospitals and clinics, are nearly always inadequate.

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Additionally, multidrug-resistant tuberculosis spreads at a higher rate among HIV-positive patients particularly in Asia and Africa, since they are immunocompromised and not all patients receive the proper treatment regimen. Tuberculosis is in fact the leading killer of HIV-positive people, killing 35 percent of patients in 2015.

Despite the high burden of disease among the poor in low- and middle-income countries, “many developing countries do not allocate funds to provide free care to such patients, and even middle-income countries do not provide patients with tuberculosis with all the necessary medicines,” Mariandyshev Andrei and Eliseev Platon of Northern State Medical University wrote in an accompanying comment.

But the problem is not just one for low- and middle-income countries. Migration and travel means drug-resistant TB can easily reach every corner of the world.

“We need to dramatically step up efforts to break the cycle of transmission – while also maintaining work to rapidly find and treat all people with tuberculosis,” Sharma said. “We must strengthen infection control measures, focus on households, health centers and communities to prevent tuberculosis spreading from person to person, and develop more effective diagnostic tests to rapidly and accurately detect drug resistance.”

Otherwise, both multidrug-resistant and extensively drug-resistant tuberculosis will increase without investment in better treatment in high burden countries, and global elimination will out of reach.

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Joanne Lu

Joanne Lu is a South Carolina-based writer and editor dedicated to global development, poverty alleviation and social justice. After a year in Rwanda, she now covers the Asia-Pacific and economics. Find her on Twitter @joannelu or email joanne@humanosphere.com.