Adult men drive global tuberculosis transmission, study finds

Tuberculosis (TB) remains one of the world’s deadliest infectious diseases, and its burden does not fall evenly across populations. Age and sex patterns in who gets sick with TB have been well documented, but until now the implications of those patterns for who is exposed to TB and who transmits it have not been systematically examined at a global scale. In a global analysis led by Katherine C. Horton, researchers combined information on how people mix socially with estimates of TB prevalence across 177 countries. Their goal was to estimate, for different age groups and for women and men, both how much exposure to TB comes from each group and how much transmission each group is responsible for. By linking social contact patterns to disease prevalence, the team aimed to move beyond simple case counts to a more dynamic picture of how TB spreads through communities. This approach allows researchers and policymakers to see not just who has TB, but who is most likely to pass it on to others, a key step for designing more effective, targeted public health responses.

The study’s method used two main pieces of information: social mixing patterns and TB prevalence measures, analyzed for 177 countries. By combining these data, the researchers estimated the proportion of TB exposure that comes from different age groups and sexes, and the proportion of transmission attributable to those same groups. Their findings were striking: across both sexes and across children and adults, a majority of estimated TB transmission was attributable to contact with adult men. When looking at age-specific patterns, exposure to TB tended to peak in adolescence — meaning teenagers have high levels of contact that could lead to exposure — but the contribution to actual transmission was either flatter across ages or increased in older age groups. These patterns varied by region, indicating that the age profile of transmission is not the same everywhere. The analysis also highlighted a sometimes overlooked role for older adults in spreading TB in certain settings, noting that older people may face specific barriers to accessing healthcare which could influence transmission dynamics.

These results have clear implications for TB control efforts. If adult men are responsible for a large share of transmission in many settings, then interventions that reduce transmission from this group — whether through improved access to diagnosis, treatment, or preventive services — could have outsized impact. The finding that exposure peaks in adolescence but transmission can be higher among older adults suggests that different age groups may require different strategies: preventing exposure among youth while ensuring timely diagnosis and care for older adults. The regional variation underlines the need for local data and context-specific planning rather than one-size-fits-all policies. The authors argue for more systematic analyses focused on the epidemiology of TB transmission so that countries can prioritize interventions based on who is actually driving transmission in their communities. Recognizing and addressing barriers to healthcare for groups like older adults will be important to reduce ongoing spread and to guide more effective, targeted public health responses.