The illusion of personal health decisions for infectious disease management: disease spread in social contact networks

Close contacts between individuals provide opportunities for the transmission of diseases, including COVID-19. Individuals take part in many different types of interactions, including those with classmates, co-workers, and household members; the conglomeration of all of these interactions produces a complex social contact network interconnecting individuals across the population. Thus, while an individual might decide their own risk tolerance in response to a threat of infection, the consequences of such decisions are rarely so confined, propagating far beyond any one person. We asses the effect of different population-level risk-tolerance regimes, population structure in the form of age and household-size distributions, and different types of interactions on epidemic spread in plausible human contact networks to gain insight into how contact network structure affects pathogen spread through a population. In particular, we find that changes in behaviour of vulnerable individuals in isolation is insufficient to reduce those individuals infection risk, that population structure can have varied and counter-acting effects on epidemic outcomes, and that, in general, interactions among co-workers have a greater contribution to disease spread than do interactions among children at school. Taken together, these results promote a nuanced understanding of disease spread on contact networks, with implications for public health strategies.