Homophily and social mixing in a small community: Implications for infectious disease transmission

community disease spread

Social networks, and the way they form strong or weak bonds, can have significant effects on epidemic potential.

As shown in the recent SARS-CoV-2 pandemic, the combination of strong ties that form communities and weak ties that bridge separate communities can create a pattern of disease spread that result in rolling peaks of cases in different communities. In other instances, when diseases spread through insular communities, the outbreak can move past a point of containment before it is noticed.

This paper, co-authored by Cook Center Associate Research Director Keisha Bentley-Edwards, also the director of the Center's Health Equity Working Group and an Associate Professor of Medicine, Division of General Internal Medicine, at Duke University, worked to understand mixing patterns across social networks in the ethnically and racially diverse community of Durham, North Carolina. The authors used a snowball sampling design to enroll people recently diagnosed with SARS-CoV-2, and asked them to describe their close contacts and recruit some contacts to enroll in the study.

Key Findings

  • The authors observed high rates of in-group mixing among ethnic/racial groups compared to the ethnic/racial proportions of the background population.
  • Black or African-American respondents interacted with a wider range of ages than other ethnic/racial groups, largely due to familial relationships, and notably interacted more with vulnerable age groups (elderly or young family members).
  • Understanding community mixing patterns can inform infectious disease risk, support analyses to predict epidemic size, or be used to design campaigns such as vaccination strategies so that community members who have vulnerable contacts are prioritized.