Evolutionary dynamics in an SI epidemic model with phenotype-structured susceptible compartment

Area of Science:

• Mathematical modeling
• Epidemiology
• Evolutionary biology

Background:

• Understanding disease dynamics requires accounting for individual variability in traits like resistance and proliferation.
• Heritable changes and fitness trade-offs are crucial evolutionary factors influencing disease spread.

Purpose of the Study:

• To develop and analyze a novel SI epidemic model incorporating continuous phenotypic variation.
• To investigate the impact of heritable changes and fitness trade-offs on disease dynamics and host adaptation.

Main Methods:

• Developed a mathematical model coupling an ODE for infected individuals with a PDE for susceptible individuals.
• Derived the basic reproduction number and characterized disease-free and endemic equilibria.
• Integrated analytical results with numerical simulations based on host-parasite experimental data.

Main Results:

• Disease spread is more likely with higher infection rates and stronger selective pressures on susceptible individuals.
• Heritable phenotypic changes can either promote or impede disease spread, contingent on pre-infection selection.
• Endemic infections with lower mortality and higher selection lead to increased host resistance and reduced phenotypic heterogeneity.

Conclusions:

• The model provides a theoretical framework for understanding the interplay between evolutionary parameters and infectious disease spread.
• Phenotypic adaptation in hosts significantly influences epidemic trajectories.
• Selective pressures exerted by pathogens drive host evolutionary responses, impacting disease outcomes.