Superspreading niches could offer novel route to faster control of TB outbreaks

Researchers argue that tuberculosis superspreading could represent both a major obstacle to disease control but also a practical opportunity to interrupt transmission earlier by targeting the social and biological settings in which highly infectious cases meet susceptible contacts

Superspreading became a familiar concept to many people during the COVID-19 pandemic but the phenomenon has long been recognised in the study of infectious disease epidemics. It describes the process by which one infected person passes an infection to an unusually large number of others. In tuberculosis (TB), the same principle has helped to explain why transmission can vary so widely between individuals and why some cases may have a disproportionately large effect on the spread and course of an epidemic.

TB is caused by infection with Mycobacterium tuberculosis. Most people with TB cause very few secondary infections and many cause none at all. However, historical studies of TB transmission, including important work carried out in the 1950s and 1960s, observed that some individuals with the disease were far more infectious and could generate many more infections among their contacts. This means that the public health value of diagnosis and the impact of early intervention of antibiotic treatment can differ considerably from person to person. Effective treatment typically makes a person with TB non-infectious within one to two weeks, so prompt identification of the most infectious cases may have a particularly strong effect on cutting levels of onward transmission.

A research team from Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA and the University of Colorado Anschutz School of Medicine, Aurora, Colorado, USA have examined historical and contemporary evidence for superspreading in M. tuberculosis transmission. They argued that superspreading represents a critical challenge for the global control of TB but also a potential opening for novel prevention strategies.

The authors introduced the concept of ‘superspreading niches’, meaning specific parts of community contact networks in which highly infectious individuals intersect with highly susceptible contacts. This framework, they suggested, could help researchers and public health teams to understand why TB transmission clusters in particular social settings and how interventions could be designed to interrupt transmission before it expands.

“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,” said senior author Dr Karen Jacobson, associate professor of medicine at Boston University.

According to the researchers, superspreading is an important but still poorly understood feature of many infectious diseases, including severe acute respiratory syndrome coronavirus 2, the virus responsible for the COVID-19 pandemic. The likelihood that any one person will transmit infection to many others depends on multiple interacting factors, including their infectiousness and the size and structure of their social contact network.

“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,” said Dr Jacobson, who is also medical director of the Boston Medical Center Tuberculosis Clinic.

Mathematical modelling studies have suggested that measures to prevent superspreading can have a particularly large effect on infectious disease epidemics. The researchers argued that the same principle may apply to TB, where targeted action against the most important transmission pathways could support continued progress against a disease that remains one of the world’s leading infectious causes of death.

The authors also emphasised that TB may be especially suited to prevention strategies focused on superspreading. Unlike directly transmitted respiratory viruses, which often cause short-lived infections that last only days, TB usually progresses more slowly. That longer disease course gives public health teams a wider window in which to identify transmission risks and deploy interventions to interrupt spread.

Treatment also offers a rapid way to reduce infectiousness. Once individuals with TB receive effective antibiotic therapy, they usually become non-infectious quickly, often within days to weeks. This means that treatment can effectively ‘turn off’ transmission from highly infectious individuals, particularly when the people most likely to transmit the disease are diagnosed promptly.

Preventive therapy could provide another important tool. People exposed to M. tuberculosis may carry the infection without yet developing active disease. In such cases, preventive treatment can reduce the risk of progression and may help to halt chains of transmission linked to superspreading niches.

The researchers concluded that a better understanding of where and why TB superspreading occurs could improve the design of control programmes. Rather than relying only on broad, untargeted approaches, future interventions may be able to focus on the people, places and contact networks where transmission risk is greatest. That strategy could make TB prevention more precise and more efficient, while preserving the central role of early diagnosis, effective treatment and preventive therapy.

For further reading please visit: 10.1016/S1473-3099(26)00168-4