Scaling of Host Competence

Body size influences many traits including those that affect host competence, the propensity to cause new infections. Here, we employ a new framework to reveal that, for at least two infections, West Nile virus and Lyme disease, large hosts should be more competent than small ones, but their lower abundance could mitigate their impacts on local risk. By contrast, for rabies, small hosts will be disproportionately more competent than large ones, an effect amplified by the higher densities of small species. These outcomes differ quite a bit from previous approaches that incorporate allometries into epidemiological models. Subsequently, we advocate for future integrative work to resolve how interspecific variation in body size influences the emergence and spread of infections.