Scientists call for innovative strategies to combat tuberculosis superspreaders

Superspreading became a familiar concept to many during the COVID-19 pandemic. Prior studies examining infectious disease epidemics, including those on COVID-19, have found that some individuals are much more likely to transmit infections to other people. Superspreading, when one person with an infection passes it to an unusually large number of other people, is a key feature of tuberculosis (TB) epidemiology.

Most individuals with TB, the disease caused by infection with Mycobacterium tuberculosis, cause very few secondary infections, and often cause no secondary infections at all. However, many studies, including groundbreaking studies in the 1950s and 1960s, examining TB transmission observed that some individuals with TB are more highly infectious and cause many more secondary infections among their contacts.

As a result, the overall impact on future transmission of diagnosing someone with TB and treating them with antibiotics (typically making them non-infectious within 1-2 weeks) can vary widely from person to person.

In a new perspective piece in The Lancet Infectious Diseases, researchers from Boston University Chobanian & Avedisian and the University of Colorado Anschutz School of Medicine examine both historical and contemporary evidence in M. tuberculosis superspreading. They argue it represents not only a critical challenge for global TB control, but also a potential opportunity for innovative prevention strategies.

The authors introduce the idea of "superspreading niches", specific parts of community contact networks where highly infectious individuals intersect with highly susceptible contacts, as a key framework for understanding TB superspreading and designing new TB control interventions.

We propose that identifying superspreading niche characteristics could allow for novel interventions directed at disrupting transmission early between highly infectious source cases and their susceptible contacts."

Karen Jacobson, MD, MPH, Study Senior Author and Associate Professor, Medicine, Boston University School of Medicine

According to the researchers, superspreading is an important yet poorly understood phenomenon observed across a wide range of infectious diseases, including SARS-CoV2 (the virus responsible for COVID-19).

"We know that multiple factors, for example, how infectious someone is, how big their social contact networks are, and other epidemiological drivers – all contribute to superspreading, but our understanding of how these factors work together remains vague and falls short of what is needed to improve public health action.There are also intriguing results from mathematical modeling studies, which suggest that preventing superspreading can have large, outsized impacts on infectious disease epidemics. This could be true for TB as well, offering an important opportunity for new TB prevention strategies that could support continued progress in the global fight against TB," adds Jacobson, who also is the medical director of the Boston Medical Center Tuberculosis Clinic.

The researchers also highlight that TB may be uniquely well-suited to superspreading-focused prevention strategies. Unlike directly transmitted respiratory viruses, where infections typically last only days, TB is a more slowly progressive disease, providing a larger window to deploy transmission-interrupting interventions.

In addition, individuals receiving effective antibiotic therapy for TB rapidly become non-infectious, typically within days, offering a quick way to "turn off" transmission from highly infectious individuals. Lastly, preventive therapy for people exposed to M. tuberculosis who have not yet developed disease is highly effective and could serve as a critical tool for halting M. tuberculosis superspreading.