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Evolution of pathogen virulence across space during an epidemic

March 1, 2015

We explore pathogen virulence evolution during the spatial expansion of an infectious disease epidemic in the presence of a novel host movement trade-off, using a simple, spatially explicit mathematical model. This work is motivated by empirical observations of the Mycoplasma gallisepticum invasion into North American house finch (Haemorhous mexicanus) populations; however, our results likely have important applications to other emerging infectious diseases in mobile hosts. We assume that infection reduces host movement and survival and that across pathogen strains the severity of these reductions increases with pathogen infectiousness. Assuming these trade-offs between pathogen virulence (host mortality), pathogen transmission, and host movement, we find that pathogen virulence levels near the epidemic front (that maximize wave speed) are lower than those that have a short-term growth rate advantage or that ultimately prevail (i.e., are evolutionarily stable) near the epicenter and where infection becomes endemic (i.e., that maximize the pathogen basic reproductive ratio). We predict that, under these trade-offs, less virulent pathogen strains will dominate the periphery of an epidemic and that more virulent strains will increase in frequency after invasion where disease is endemic. These results have important implications for observing and interpreting spatiotemporal epidemic data and may help explain transient virulence dynamics of emerging infectious diseases.

Citation Information

Publication Year 2015
Title Evolution of pathogen virulence across space during an epidemic
DOI 10.1086/679734
Authors Erik E. Osnas, Paul J. Hurtado, Andrew P. Dobson
Publication Type Article
Publication Subtype Journal Article
Series Title American Naturalist
Series Number
Index ID 70155019
Record Source USGS Publications Warehouse
USGS Organization Patuxent Wildlife Research Center

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