Social divisions and risk perception drive divergent epidemics and large later waves

Abstract

During infectious disease outbreaks, individuals may adopt protective measures like vaccination and physical distancing in response to awareness of disease burden. Prior work showed how feedbacks between epidemic intensity and awareness-based behavior shapes disease dynamics. 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 develop a compartmental model of disease transmission and awareness-based protective behavior 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). Using simulations, we show that groups that are more separated in awareness have smaller differences in mortality. Fatigue (i.e., abandonment of protective measures over time) 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. Counterintuitively, 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 therefore vaccine uptake. Awareness-based protective behavior, including awareness separation, can fundamentally alter disease dynamics.

Age classes stratified by risk and adaptive behavior during epidemics

“…It is worth noting that the justification for the bifurcated structure need not be restricted to age-based differentiation, but can also include political party affiliation, income levels, or other demographic, social, behavioral, physical, or geographic differences. Some studies use structured 2-population models with varying homophily and outgroup aversion or varying awareness separation and mixing separation [40,41]. Results from these models indicate that heterogeneous populations, even when simply structured compartmentally as two populations, can produce greater complexity in epidemic dynamics, including large second waves and interconnected dual epidemics.…”

Age-differentiated incentives for adaptive behavior during epidemics produce oscillatory and chaotic dynamics

“…It is worth noting that the justification for the bifurcated structure need not be restricted to agebased differentiation, but can also include political party affiliation, income levels, or other demographic, social, behavioral, physical, or geographic differences. Some studies use structured 2-population models with varying homophily and outgroup aversion or varying awareness separation and mixing separation [40,41]. Results from these models indicate that heterogeneous populations, even when simply structured compartmentally as two populations, can produce greater complexity in epidemic dynamics, including large second…”

Founder effects arising from gathering dynamics systematically bias emerging pathogen surveillance

“…During infectious disease outbreaks individuals may vary in how much they alter their behavior in response to perceived risk [30, 8, 2, 15]. To capture this we can further generalize the group-SIR dynamics where individuals choose among differently sized, concurrent gatherings and avoid those larger than their “risk level”: where risk levels are denoted by subscripts.…”