In 1910, when the best available treatment for tuberculosis was fresh air, clean surroundings, good food and rest, the Royal Ottawa Sanatorium opened its doors, allowing area TB sufferers to stay in the city, rather than be sent away to Muskoka. Since that time, TB has been all but eliminated in Ottawa, and the University of Ottawa Institute of Mental Health Research now stands on the site of the old sanatorium.
But elsewhere in the world—and even in Canada—tuberculosis continues its insidious spread. Epidemiologist and health economist Dr. Alice Zwerling, assistant professor at the Faculty of Medicine’s School of Epidemiology and Public Health, is fighting a tide that has become even higher this year as COVID scared people away from health facilities and caused a setback in TB progress estimated at more than a decade.
Tuberculosis and humans go way back. Scientists have found tuberculosis bacteria in Egyptian mummies, and in recent decades—before the COVID-19 pandemic swept the globe—it had risen to become the number one infectious disease killer with 1.4 million annual deaths attributed either to TB alone or to a devastating combination of TB and HIV. While great strides have been made in the prevention and treatment of other longtime human diseases like, say, malaria, neither good, rapid point-of-care diagnostics nor short-course treatments exist for tuberculosis.
That’s because of the uniquely tricky issue of latency in TB. Somewhere around one-third of the world’s population carries within them a latent TB infection that will most likely never flare up into symptoms. For researchers, that means trying to get a handle on some two-and-a-half billion people who have the potential to develop TB sometime in the next 80 years or so, even if they never again encounter another person with TB.
Dr. Zwerling’s work spans home and abroad. In Canada, her team is looking at the cost-effectiveness of interventions in Nunavut, where the territorial government is working to tackle one of the most challenging tuberculosis problems in the country. They are pursuing a path that the WHO recently recognized as the best hope of TB elimination: active case-finding and preventive treatment.
The aim is to prevent latent TB from becoming active, and thus both harmful to the host and contagious, in the first place. The benefits of such an approach would be felt for decades to come. Zwerling’s team has been studying a prevention regimen that would only require 12 visits to a health clinic rather than more than 100 daily visits that are required in standard prevention programs.
Tuberculosis is known as a disease of poverty, largely because the difference between a latent case and an active one often comes down to the state of the immune system. Vulnerable populations with high rates of smoking, diabetes, malnutrition or HIV are more susceptible to develop active disease.
“Typically, an immunocompetent individual would only have about a 5-10% lifetime risk of developing active TB, but in individuals who are immunocompromised, like with HIV, for example, that risk increases dramatically to about a 5-10% annual risk,” says Dr. Zwerling. “Furthermore, there is no gold standard or accurate test for latent TB infection. We have much better diagnostics for COVID, for example.”
In her global health work, in addition to working with WHO groups on guideline development and systematic reviews, Dr. Zwerling’s team is involved in an international collaboration looking at preventatively treating children and adolescents living with HIV in five African countries where TB is endemic.
“While the larger project is a cluster randomized trial, my team at the University of Ottawa are leading the economic evaluation of that, trying to understand the cost and cost-effectiveness of providing these regimens and preventive treatment to larger populations in Africa,” says Dr. Zwerling.
Economic evaluations are a critical component because tuberculosis research, treatment and prevention programs are so cash-strapped and the investments required are considerable. If Dr. Zwerling’s team can demonstrate the benefits in reduced transmission and incidence, governments and other policymakers can justify those expenditures.
“We have such a limited amount of resources in TB that we have a higher responsibility to use those resources wisely,” says Dr. Zwerling. “There’s simply no excuse for wastage.”
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