Social divisions and risk perception can drive divergent epidemic dynamics and large second and third waves

Abstract

AbstractDuring infectious disease outbreaks, individuals may adopt protective measures like vaccination and physical distancing in response to awareness of disease burden. Prior work showed how feedback between epidemic intensity and awareness-based behavior shapes disease dynamics (e.g., producing plateaus and oscillations). These models often overlook social divisions, where population subgroups may be disproportionately impacted by a disease and more responsive to the effects of disease within their group. We hypothesize that socially divided awareness-based behavior could fundamentally alter epidemic dynamics and shift disease burden between groups.We develop a compartmental model of disease transmission in a population split into two groups to explore the impacts of awareness separation (relatively greater in-versus out-group awareness of epidemic severity) and mixing separation (relatively greater in-versus out-group contact rates). Protective measures are adopted based on awareness of recent disease-linked mortality. Using simulations, we show that groups that are more separated in awareness have smaller differences in mortality. Fatigue-driven abandonment of protective behavior can drive additional infection waves that can even exceed the size of the initial wave, particularly if uniform awareness drives early protection in one group, leaving that group largely susceptible to future infection. Finally, vaccine or infection-acquired immunity that is more protective against transmission and mortality may indirectly lead to more infections by reducing perceived risk of infection, and thereby reducing vaccine uptake. The dynamics of awareness-driven protective behavior, including relatively greater awareness of epidemic conditions in one’s own group, can dramatically impact protective behavior uptake and the course of epidemics.