Higher-order interactions on disease transmission can reverse the dilution effect or weaken the amplification effect to unimodal pattern

Abstract

Determining whether species richness protects host species against infectious diseases transmission (i.e., dilution effect) within established communities is a core concern of disease ecology. Previous modeling studies have focused on pairwise transmission between hosts, largely ignoring the impact of neighboring species on pathogen transmission. Here, we modified the multi-host susceptible-infected-recovered (SIR) model to investigate the effects of higher-order interactions on the dilution effect. We found that compared with direct transmission, higher-order interactions that impede pathogen transmission can disproportionately decrease disease risk at high species richness levels under additive community assembly and thereby enhance a dilution effect or neutralizing an amplification effect into a unimodal species richness-disease relationship. Conversely, higher-order interactions that promote infection among host neighbors can enlarge an amplification effect and diminish a dilution effect or even reverse it. Higher-order interactions did not affect the emergence of the dilution effect for substitutive community assembly. Our results provide a unified framework for understanding the dilution and amplification effects and emphasize the importance of taking higher-order interactions into account for understanding mechanisms underlying the dilution effect.