Research On The Relationship Between Theoretical And Empirical Indicators Of Disease Risk In A Multi-host Pathogen System

Many empirical and theoretical indicators have been proposed to measure epidemic size and disease risk.Studies have suggested that these indicators may respond differently to risk factors such as changes in host species richness.However,the relationships between these indicators remain poorly understood.By incorporating ecological realism and a multi-host SIR?susceptible-infectious-recovered?model and SI?susceptible-infectious model?,we here first investigate the responses of theoretical measures?e.g.,community R₀ and community competence?and empirical measures?e.g.,infection prevalence and the number of infected hosts?to the changes in host species richness in systems with different transmission types.Our results indicate that different measures respond differently to host species richness for both density-dependent and frequency-dependent transmission.We then explore the relationships between theoretical measures?e.g.,community R₀ and community competence?and empirical measures?e.g.,infection prevalence and the number of infected hosts?.We show that the performance of different theoretical indicators in explaining these empirical measures depended on transmission type?density-dependent or frequency-dependent?and on the relative strength of interspecific transmission.Particularly,community competence correlates badly to empirical measures and is thus not a good indicator of disease risk.Therefore,we propose a new index,the full community competence index,which performs better than community R₀ in explaining empirical measures in frequency-dependent transmission with low interspecific transmission.This study contributes to a better understanding of the diversity-disease relationships,and addresses how to better quantify disease risk in multi-host pathogen systems.