Paradoxes in the co-evolution of contagions and institutions

Epidemic models study the spread of undesired agents through populations,
be it infectious diseases through a country, misinformation in social
media, or pests infesting a region. In combating these epidemics, we rely
neither on global top-down interventions, nor solely on individual
adaptations. Instead, interventions commonly come from local institutions
such as public health departments, moderation teams on social media
platforms, or other forms of group governance. Classic models, which are
often individual or agent-based, are ill-suited to capture local
adaptations. We leverage developments of institutional dynamics based on
cultural group selection to study how groups attempt local control of an
epidemic by taking inspiration from the successes and failures of other
groups. Incorporating institutional changes into epidemic dynamics reveals
paradoxes: a higher transmission rate can result in smaller outbreaks as
does decreasing the speed of institutional adaptation. When groups
perceive a contagion as more worrisome, they can invest in improved
policies and, if they maintain these policies long enough to have impact,
lead to a reduction in endemicity. By looking at the interplay between the
speed of institutions and the transmission rate of the contagions, we find
rich co-evolutionary dynamics that reflect the complexity of known
biological and social contagions.