The Demographic Transition, Social Network Change, and the Size of the West African Ebola Outbreak

Ashton M. Verdery, University of North Carolina at Chapel Hill
Nalyn Siripong, University of North Carolina at Chapel Hill
Jonathan Daw, University of Alabama at Birmingham
James Moody, Duke University

Why is the current Ebola outbreak in West Africa orders of magnitude larger than any seen before? Here we examine the size and structure of family networks – the sorts of close personal relations needed to carry a disease transmissible only by close contact with bodily fluids. Using network simulation methods, we find that demographic changes experienced in West Africa have led to a rapid increase in numbers of living family members which now supports large, globally connected kinship networks. Prior Ebola outbreaks occurred in areas and times that corresponded to small fragmented networks. In this context, features of these countries’ demographic transitions play a crucial role by generating a rapid growth in living family sizes that pushed community-level network structures past the connected component phase transition. This creates opportunities for a broad, fast moving outbreak that can spread far in the network solely through family contact.