Characterizing social behavior relevant for tuberculosis transmission in four low- and middle-income countries

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (Mtb), a bacterium which is transmitted through the air. Close, sustained contact can lead to transmission of Mtb, but evidence also shows that transmission occurs also in community settings through more transient contact. However, social patterns that influence Mtb transmission, and locations that are most central to spread, are likely different by setting.

We use data from the GlobalMix study, which characterized social behavior across four countries, to evaluate differences in age-sex patterning and locations of contact across four moderate- to high-TB burden countries. Healthy individuals self-completed a survey about their daily person-to-person interactions and locations in which they spent time. To capture the Mtb exposure profile of participants, we calculated daily exposure-hours from household contacts, close non-household contacts, and casual contacts, stratified by contact age and sex, and weighted by country-, age-, and sex-specific tuberculosis incidence estimates.

The most prominent shifts in the profile of exposure occur at entry to primary school (5-9 years) and early adulthood (20-29 years). Community locations varied in their relative importance as locations of transmission by country and age group, with school most important in India and Guatemala, transit more important in Pakistan, and others' homes most important in Mozambique.

Our findings demonstrate that locations of community transmission are likely varied across settings, underscoring the importance of interventions designed specifically for the communities in which they will be implemented.