We describe social behaviors relevant for transmission of enteric and respiratory infections in four low- and middle-income countries across three continents, with an emphasis on children under 5 years of age. Mean daily contact rates were highest among school-aged children in every country and tended to be higher in rural sites. Important non-home locations for contact varied across countries. Among children under 5 years of age, contacts with non-household members occurred primarily at home and ‘other’ locations. Overall, we show that patterns of social interaction are broadly similar across countries, but key differences, including within-country rural-urban variation and the relative importance of non-home locations, could have implications for transmission dynamics of enteric and respiratory infections and the effectiveness of interventions aiming to limit their spread.
Daily contact rates reported in this study are within range of some reported in the UK21 and Zimbabwe22, but overall lower than previous estimates. In a recent review and meta-analysis, the mean number of contacts per day reported across studies conducted from 2005 to 2018 in 22 countries, was 14.5 contacts20. It is notable that our estimates are low despite using prospective data collection and use of paper questionnaires, which have been shown to more fully ascertain contacts than other survey methods23. The timing of our study may partially account for fewer reported contacts, given the protracted impact of the COVID-19 pandemic on social behavior. Mozambique and Guatemala were likely most affected given the overlap of pandemic mitigation measures with data collection periods in 2021. However, despite official changes in pandemic mitigation policies that occurred during these periods, we show that the number of contacts reported was relatively stable through multiple months of data collection in each site. (Supplementary Figs. 9–12) This is consistent with anecdotal reports from field staff that while some policies to limit dense public gatherings were still in place through 2021, these restrictions were no longer meaningfully impacting daily interactions of most community members. Lower rates of contact could also stem from our household-based method of recruitment, which could have led us to recruit individuals who were more likely to be unemployed or otherwise less engaged in communal activities. Finally, it is also possible that contact rates have truly declined in recent years, given the widespread use of mobile smartphones and other technologies that have weakened social connections and reduced the frequency of in-person interactions.
Variations in the nature and number of contacts by country may reflect social, cultural, economic and even climactic differences. While the proportion of physical contacts reported in our study overall was similar to that reported in other low- and middle-income countries20, we report a particularly high proportion of physical contacts in Pakistan. This likely reflects customs of greeting friends and acquaintances that often involve touch, especially among men. (Men in Pakistan also reported substantially more contacts than women, which may reflect gendered religious and social norms that govern common interaction.) In Mozambique, more interactions were reported outdoors than in other countries. This may reflect the influence of climate, which in southern Mozambique features mild temperatures that fluctuate little through the year, and differences in the built environment that encourage congregating outside. All of these differences may influence the speed and patterns of spread of infections and can be used to better understand behaviors to target for intervention that may vary across settings.
In two of four countries, rural contact rates were substantially higher than in urban areas, a counterintuitive result that may reflect the relative closeness of community structure in rural areas despite lower population density. Our findings are generally consistent with other studies, some of which show higher contact rates in rural vs peri-urban participants16,24, and others4,25 which do not show differences. Understanding variation in contact patterns in rural and urban settings is particularly important when modeling the spread of new infections, which are often initially introduced into well-connected urban centers and diffuse more slowly to rural areas.
While we found similar rates of contact as reported previously for infants and young children26,27, our study provides additional detail on changes of children’s contact patterns from birth to age 5, a critical period of vulnerability to infectious disease. Across countries, the majority of children’s contacts are reported at home. However, the proportion of contacts occurring at home falls steadily from birth to age 5 in Guatemala and India and remains more stable in Mozambique and Pakistan. Patterns in biological susceptibility to infection change during this period, as maternally derived immunity wanes and the innate immune system matures28. Our data demonstrate the social changes that occur in parallel and shape exposure to pathogens in early childhood, and thereby risk of infection and illness in this age group28. Importantly, our study also differentiates contacts that occur at home and those that occur with household members. For children under 5 years of age, the two most important locations of exposure to non-household contacts were in their own homes and in Other locations. These patterns likely reflect sociocultural differences in caregiving practices for young children across countries, which can shape transmission patterns among children or between children and caregivers.
Similar to previous surveys18, we find the highest rates of contact among school-aged children and the highest rates of assortative mixing among adolescents (10–19-year-olds). The relative importance of contacts in schools across settings can inform context-specific predictions of the effectiveness of school closings and other policies that may limit school attendance to prevent spread of infection, especially given the great social costs of such interventions on children and communities.
While POLYMOD-based projections show broadly similar patterns of contact by age across the four countries; our estimates show differences in age patterns by country. POLYMOD-based projections tend to overestimate contacts at work and underestimate contacts at home, consistent with previous literature that has shown that people in LMIC have more contacts at home and fewer contacts at work than in high-income countries20. When we used our empirical data to model the spread of an emerging pathogen in each site, we found that cumulative incidence varied substantially, with sites reporting lower contact rates displaying lower incidence. In Pakistan, qualitative differences in contact patterns by age led to higher incidence among young children in the rural site as compared to the urban site. Compared to the epidemic simulated using POLYMOD-based projections of contact patterns, we saw qualitatively different patterns by age in cumulative incidence of infection, with substantially more variation by age in simulations using the GlobalMix data and a generally slower progression of the epidemic. Though this modeling exercise was based on simple assumptions which would need to be adjusted to better capture the more complex natural history of most enteric and respiratory pathogens, it illustrates that using context-specific data can lead to different inferences about how pathogens will spread and affect demographic sub-populations.
There were some limitations to this study. Information on children’s contacts were recorded using ‘shadows’, or individuals who recorded contacts on behalf of the participant. This may have led to inaccuracies since we do not know how completely shadows observed children’s contacts. Second, we defined contact as an interaction involving three or more words with another person at distance of an arm’s length. More transient interactions, which include being near a person in a crowded public place without speaking to them, are not captured by this definition. However, closer contacts are likely more important for transmission and allowed for comparison with previous work18. Third, these data should not be considered representative of each country. They can be considered representative of each site, since we adjusted overall contact rates for age and sex population distributions at each site. We recruited at multiple sites per country to capture at least some variation in contact patterns associated with varying population density within each country. Finally, we recruited participants over a limited time frame at each site, so could not capture seasonal variations in contact patterns that may be important for transmission (i.e., holidays, school start and end). One previous study in India has documented a higher number of contacts in the winter season relative to the monsoon or summer seasons; however, these differences were slight32.
This study represents the first effort to collect and compare social contact data using standardized tools across multiple LMIC, with a special focus on contact patterns among children under 5 years of age. These data can inform future modeling efforts aiming to accurately capture behavioral patterns that drive the speed and patterns of spread of infections in different contexts, and to estimate the impact of interventions targeting a broad range of pathogens.
