Tuberculosis (TB) is one of the leading causes of death around the world. Despite the fact that TB is preventable and treatable, it is estimated that approximately 25% of the world’s population has a latent infection that might progress to TB disease. Furthermore, this disease seems to have male-bias — it is more commonly found in men than women. In this study by Miller and colleagues, researchers sought to figure out how social-mixing within and across people’s social contact networks affects the likelihood of males developing TB.
This study took place in the Rubaga region of Kampala, Uganda where the rate of TB disease is among the highest in the world. Researchers recruited and identified index cases (people who present with TB disease) within the region and collected the demographic information and relationship status for each. Once index cases had been recruited, age and sex-based community controls were recorded and people without TB disease were recruited. Index cases and control participants were then interviewed to identify their social networks using a sampling protocol called “egocentric network sampling”.
The social networks for index cases and control participants were compared to obtain social network centrality statistics between males and females and between index cases and controls. Theory predicts that Individuals with higher network centrality will become infected faster and more often than those with lower network centrality because central individuals are a smaller number of steps away from the average individual than less central individuals. Researchers also analyzed patterns of sex- assortativity, or how often individuals interact with those of the same sex. It was hypothesized that sex-assortativity may lead males to have higher exposure to others with infectious TB.
This surprising finding of this study was that there were no major differences in key social network centrality statistics between index case and control participants or between males and females. However, it was found that having more male contacts within one’s social network leads to greater likelihood of being exposed to and developing TB.
By comparing networks of males and females and index cases and controls, Miller et al. were able to gain greater understanding of the male-bias infection patterns of TB. The researchers found that males did have higher levels of contact between other males and individuals who had recently been diagnosed with TB. This offers new insight that social-mixing patterns within a region can drive male-bias in TB. For more information on this study, please visit https://doi.org/10.1186/s12879-021-06475-z .
Miller, P.B., Zalwango, S., Galiwango, R. et al. Association between tuberculosis in men and social network structure in Kampala, Uganda. BMC Infect Dis 21, 1023 (2021). https://doi.org/10.1186/s12879-021-06475-z