New method identifies communities experiencing drug-resistant tuberculosis in South Africa

Researchers at Boston Medical Center (BMC) have created a near real-time surveillance method to identify communities experiencing a high burden of drug-resistant tuberculosis in South Africa using routinely collected laboratory data. The team mapped where in the Western Cape Province were the highest rates of drug-resistant tuberculosis and tracked changes over five years. The results of this study, published in PLOS Medicine, will help create a method that can lead to more targeted interventions and public health approaches aimed at reducing the number of people who contract the disease.

South Africa has the highest rates of tuberculosis (TB) incidence in the world, with 4 percent of those cases being multidrug resistant cases, meaning resistant to first line treatment. The country also has a centrally collected laboratory database that includes TB tests, making it an ideal location to implement a surveillance system to track drug- resistant TB cases by clinic location. Researchers developed an algorithm to identify unique patients and episodes of disease from the data, and created heat maps of the region to see which areas were most afflicted between 2008 and 2013.

The group identified 799,779 individuals who had specimens submitted for TB tests from clinics during the study period; 28% were diagnosed with TB, of which 4.6 percent were resistant to first line tuberculosis treatment. The spread of these cases was geographically heterogeneous, ranging from zero to 25 % of TB cases having drug resistance in different parts of the region. There were also significant annual fluctuations in drug-resistant TB percentages at several locations. The communities that saw the highest rates of drug-resistant TB were Cape Town townships and informal settlements, the rural region of the west coast, and areas bordering the Eastern Cape Province.

"It is critically important that we understand how drug-resistant TB impacts people in specific areas over time," says Karen Jacobson, MD, MPH, infectious disease physician at BMC. "By locating emerging and chronic hotspots of the disease in real-time, public health providers can evaluate the most effective interventions and monitor progress towards TB reduction goals."

Researchers also emphasize the role routinely collected laboratory data plays in identifying both ongoing and short-term TB outbreaks. Their findings show this data is a powerful tool for researchers and providers, allowing for more accurate allocation of resources to treat TB.

Recent evidence shows that the TB epidemic is dynamic, and that medication-resistant TB infections are spread through transmission from another individual with drug-resistant TB disease. This indicates that constant monitoring could lead to more effective public health interventions, resulting in fewer cases of medication-resistant TB.

"Our model of mapping high-burden communities can serve as a roadmap for regions working to reduce TB incidence by initiating treatment as soon as possible," says Jacobson, who also is an assistant professor of infectious diseases and epidemiology at Boston University School of Medicine and Boston University School of Public Health, respectively.