Persistence-infectivity trade-offs in environmentally transmitted pathogens change population-level disease dynamics

TL;DR

This study models how trade-offs between pathogen persistence in the environment and infectivity influence disease outbreak dynamics, highlighting the importance of monitoring pathogen subpopulations for better risk assessment.

Contribution

It introduces a modeling framework demonstrating the impact of persistence-infectivity trade-offs on epidemic progression and emphasizes the need for improved environmental monitoring methods.

Findings

Less infectious, more persistent pathogens slow epidemic progression.

Standard surveillance data insufficient to reveal underlying pathogen dynamics.

Identifiability analysis highlights challenges in monitoring pathogen subpopulations.

Abstract

Human pathogens transmitted through environmental pathways are subject to stress and pressures outside of the host. These pressures may cause pathogen pathovars to diverge in their environmental persistence and their infectivity on an evolutionary time-scale. On a shorter time-scale, a single-genotype pathogen population may display wide variation in persistence times and exhibit biphasic decay. Using an infectious disease transmission modeling framework, we demonstrate in both cases that fitness-preserving trade-offs have implications for the dynamics of associated epidemics: less infectious, more persistent pathogens cause epidemics to progress more slowly than more infectious, less persistent (labile) pathogens, even when the overall risk is the same. Using identifiability analysis, we show that the usual disease surveillance data does not sufficiently inform these underlying pathogen population dynamics, even with basic environmental monitoring. These results suggest directions for future microbial research and environmental monitoring. In particular, determining the relative infectivity of persistent pathogen subpopulations and the rates of phenotypic conversion will help ascertain how much disease risk is associated with the long tails of biphasic decay. Alternatively, risk can be indirectly ascertained by developing methods to separately monitor labile and persistent subpopulations. A better understanding of persistence--infectivity trade-offs and associated dynamics can improve risk assessment and disease control strategies.