Acknowledgments
The authors would like to thank members of the OGPlexus for helpful discussions and input on all aspects of the manuscript. In particular, we thank M.M.D. and A.L.M. for especially helpful interactions.

Supplementary Materials
The following are available online at https://www.mdpi.com/1999-4915/12/9/1055/s1. Table S1. Fixed parameters, and their references. Table S2. Alternative virulence definition containing only items that directly affect host well-being (fitness). Figure S1. Alternative virulence definition: The impact of varying virus virulence and survival assessed on four key epidemic metrics. Figure S2. Alternative virulence definition: The percent change in SEAIR-W outbreak metrics as survival increases from −5% to +5% for different virulence-survival relationships (positive correlation and negative correlation). Figure S3. Alternative virulence definition: Virus outbreak dynamics for the extreme values of virulence and free-living survival considered for the two hypotheses. Table S3. Alternative virulence definition: Comparing epidemic metrics under low survival/low virulence versus high survival/high virulence scenarios. Table S4. Alternative virulence definition: Comparing epidemic metrics under low survival/low virulence versus high survival/high virulence scenarios (as in the negative correlation scenario). Figure S4. Side by side comparison of the main text virulence definition (A1 → D1) and alternative definition of virulence (A2 → D2). Figure S5. Side by side comparison of the main text virulence definition (left) and alternative definition of virulence (right). Figure S6. Side by side comparison of the main text definition (A1 → H1) and supplemental definition of virulence (A2 → H2).
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Author Contributions
Conceptualization, L.M.G., W.C.T. and C.B.O.; methodology, V.A.M. and C.B.O.; software, V.A.M.; validation, V.A.M. and C.B.O.; formal analysis, L.M.G., V.A.M., W.C.T. and C.B.O.; investigation, L.M.G., V.A.M., W.C.T. and C.B.O.; resources, C.B.O.; data curation, L.M.G and V.A.M.; writing—Original draft preparation, L.M.G., V.A.M., W.C.T. and C.B.O.; writing—Review and editing, L.M.G., V.A.M., W.C.T. and C.B.O.; visualization, V.A.M.; supervision, C.B.O. and W.C.T.; project administration, C.B.O.; funding acquisition, N/A. All authors have read and agreed to the published version of the manuscript.

Funding
This research received no external funding.

Conflicts of Interest
The authors declare no conflict of interest.