Systematic shifts in the variation among host individuals must be considered in climate-disease theory

To make more informed predictions of host-pathogen interactions under
climate change, studies have incorporated the thermal performance of host,
vector, and pathogen traits into disease models to quantify effects on
average transmission rates. However, this body of work has omitted the
fact that variation in susceptibility among individual hosts affects
disease spread and long-term patterns of host population dynamics.
Furthermore, and especially for ectothermic host species, variation in
susceptibility is likely to be plastic, influenced by variables such as
environmental temperature.For example, as host individuals respond
idiosyncratically to temperature, this could affect the population-level
variation in susceptibility, such that there may be predictable functional
relationships between variation in susceptibility and
temperature.Quantifying the relationship between temperature and
among-host trait variation will therefore be critical for predicting how
climate change and disease will interact to influence host-pathogen
population dynamics. Here, we use a model to demonstrate how short-term
effects of temperature on the distribution of host susceptibility can
drive epidemic characteristics, fluctuations in host population sizes, and
probabilities of host extinction. Our results emphasize that more research
is needed in disease ecology and climate biology to understand the
mechanisms that shape individual trait variation, not just trait averages.