Santa Fe Institute

Biology, behavior, and disease

Wild Erythrocebus patas monkey captured in Senegal (mouse over for more)

The spread of disease is an emblematic example of a complex adaptive system, as it encompasses many agents reacting and adapting to one another in ways that result in emergent, hard-to-predict behaviors at the system level. A pathogen’s evolutionary trajectory (or path), its interactions with other pathogens, the environment, a hosts’ behaviors, and the effects of interventions are just a few of the many interacting systems that influence how a disease spreads through a population – and whether it becomes an epidemic.

Our project’s goal is to construct a complex adaptive systems framework for investigating disease. With multidisciplinary tools from complex systems, we can mathematically explore why certain communities are more vulnerable or more resilient to specific diseases than others, for example. We can test competing explanations for the resurgence of pathogens like Bordetella pertussis — the primary causative agent of whooping cough — in a vaccinated population. We can understand the overlapping causative mechanisms behind the Ebola virus outbreak in West Africa.

Why is developing such an approach to studying disease at the Santa Fe Institute potentially transformative, both scientifically and from a public health perspective? Simply put, the most salient and challenging features of disease are emergent properties: from the observed health disparity in low socio-economic regions to the long-term cyclicity of dengue virus infections. In the context of complex adaptive systems, emergence refers to the collective behavior that cannot be predicted from the behavior of individual components. Therefore our goal is to understand the gestalt of disease, something that researchers at the Santa Fe Institute are qualified and well-positioned to accomplish.

Models constructed using this complex adaptive systems framework can more accurately predict the spread of an outbreak and project its future course. Perhaps more important, a richer understanding of diseases and their causes can inform effective interventions and better prepare our global community for the next would-be pandemic. More