Modelling the effect of within-host dynamics on the diversity of a multi-strain pathogen
Nefel Tellioglu1, Nicholas Geard2, Rebecca H Chisholm3
1School of Computing and Information Systems, The University of Melbourne, Australia.
Abstract:
Multi-strain pathogens such as Group A Streptococcus, Streptococcus pneumoniae, and Staphylococcus aureus cause millions of infections each year with a substantial health burden. Control of multi-strain pathogens can be complicated by the high strain diversity often observed in endemic settings. It is not well understood how high strain diversity is maintained in populations, given that they compete with each other both directly (within an individual host) and indirectly (via host immunity). Previous modelling studies have investigated how indirect competition affects the prevalence and diversity of strains. However, these studies often make simplifying assumptions about the direct competition that occurs within hosts. Currently, little data is available to validate these assumptions, hence there is a need to clarify how sensitive model outputs are to these assumptions. In this study, we compare the dynamics of multi-strain pathogens under different assumptions about direct competition between strains using an agent-based model. We find that the assumptions made about direct competition can affect the epidemiological dynamics, particularly when there is no long-term immunity following infections and a low rate of importation of non-circulating strains. Our results suggest that while direct and indirect competition can each decrease strain diversity when they act in isolation, they may increase strain diversity when they act together. This finding highlights the importance of examining sensitivity to assumptions about strain competition. In particular, omitting consideration of direct competition can lead to inaccurate estimates of the likely effectiveness of control strategies as changes in strain diversity shift the level of direct strain competition.
Insights
Understanding pathogen competition is key to controlling multi-strain infections. Direct and indirect competition can unexpectedly increase strain diversity when acting together, impacting control strategies.
Area of Science:
- Epidemiology
- Mathematical Biology
- Infectious Disease Dynamics
Background:
- Multi-strain pathogens like Group A Streptococcus, Streptococcus pneumoniae, and Staphylococcus aureus cause significant global health burdens.
- High strain diversity in endemic settings complicates pathogen control, with mechanisms of maintenance under direct and indirect competition poorly understood.
- Existing models often simplify direct within-host competition, lacking data for validation and raising concerns about sensitivity analysis.
Purpose of the Study:
- To investigate how different assumptions about direct competition between pathogen strains influence epidemiological dynamics.
- To assess the sensitivity of multi-strain pathogen models to assumptions regarding direct competition.
- To clarify the interplay between direct and indirect competition in maintaining pathogen strain diversity.
Main Methods:
- Utilized an agent-based model to simulate multi-strain pathogen dynamics.
- Compared model outcomes under varying assumptions of direct competition between strains.
- Analyzed scenarios with and without long-term immunity and varying rates of strain importation.
Main Results:
- Assumptions about direct competition significantly impact epidemiological dynamics, especially with no long-term immunity and low strain importation rates.
- While isolated direct or indirect competition can reduce strain diversity, their combined effect may increase it.
- Omitting direct competition can lead to inaccurate predictions of control strategy effectiveness due to altered strain diversity.
Conclusions:
- The interplay between direct and indirect competition is crucial for understanding pathogen strain diversity.
- Agent-based models are valuable for exploring complex competitive interactions in pathogen populations.
- Accurate modeling of direct competition is essential for developing effective public health interventions against multi-strain pathogens.
Related Concept Videos
01:09Mutation, Gene Flow, and Genetic Drift
01:23Mechanistic Models: Compartment Models in Individual and Population Analysis
01:27Diversity of Protists IV
01:27Diversity of Protists II
01:27Diversity of Protists III
02:39Gene Flow