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Globally, 3 in every 1,000 people carry latent MDR-TB
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Researchers estimated that, globally, three in every 1,000 people carry latent multidrug-resistant tuberculosis, or MDR-TB, with the prevalence being 10 times higher among children younger than 15 years of age, according to a study published in The Lancet Infectious Diseases.
“Tuberculosis is the infectious disease responsible for the most deaths worldwide. The complex natural history of Mycobacterium tuberculosis means that, for ultimate disease control, people with latent infections need to be targeted,” Gwenan M. Knight, PhD, assistant professor in the department of infectious disease epidemiology at the London School of Hygiene & Tropical Medicine, and colleagues wrote. “As much as 23% of the world’s population could have latent tuberculosis infection, and, even if transmission stopped in 2014, reactivation disease would overwhelm the 2035 End TB targets.”
According to the study, Knight and colleagues used WHO data to create a model to estimate national trends in the proportion of new TB cases caused by MDR strains.
The findings showed that, in 2014, 19.1 million people were latently infected with MDR-TB, resulting in a global prevalence of .3%, Knight and colleagues reported. MDR strains accounted for 1.2% of the total latent TB burden and 2.9% of the burden among children younger than 15 years of age. The researchers estimated that 1.9 million people globally were at high risk for active MDR-TB in 2015.
Knight and colleagues warned that the proportion of latent TB caused by MDR strains will increase if current trends continue, posing “a serious challenge” for the management of latent TB.
“Targeting latent tuberculosis infection is essential for tuberculosis elimination, but standard preventive treatment regimens are probably ineffective against latent MDR strains,” they wrote. “The estimates for the proportion of latent tuberculosis infections caused by MDR strains, and associated variations by setting and age we have provided should help to inform clinical decision-making about regional preventive treatment regimens for latent MDR tuberculosis in children younger than 15 years.”– by Caitlyn Stulpin
Disclosures: The authors report no relevant financial disclosures.
Perspective
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David L. Cohn, MD
The findings of the mathematical modeling study by Knight and colleagues about the global prevalence of latent MDR-TB infection are not surprising. We have known for some time that MDR-TB (and therefore latent MDR-TB) has been around for a while and is getting worse. What the study does show are more precise estimates of latent MDR-TB by age and geographic areas and trend analysis. These data provide information that can potentially be used in the future by WHO and others for planning and targets related to MDR-TB control efforts, and advocacy to ensure the political will and funding to tackle this problem.
The important question is what can be done now to possibly halt or reverse the trends of these worrisome data? The approach to the control of drug-resistant TB is the same as that for drug-sensitive TB (albeit more challenging): rapid and accurate detection of TB disease; safe and effective treatment to prevent morbidity, mortality and transmission leading to latent TB; and safe and effective therapy of latent TB. Major advances have occurred in the past decade related to diagnosis. And new drugs have been approved and now used for treatment of MDR-TB with shorter, less toxic regimens than have been used in the past.
But the widespread use of preventive therapy for treatment of presumed drug-sensitive latent TB with isoniazid, rifampin and/or rifapentine has not been implemented in most countries of the world, and the treatment of latent MDR-TB (ie, contacts of MDR-TB) is virtually nonexistent. As mentioned in the article, there are now clinical trials underway to evaluate levofloxacin and delamanid. The results of the TB-CHAMP and V-Quin trials of levofloxacin are expected in 2020 and 2022, respectively, and of the recently started PHOENIX trial of delamanid in 2025. Stay tuned — we are in this for the long haul.
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