Cross-scale dynamics and the evolutionary emergence of infectious diseases

Sebastian J. Schreiber; Ruian Ke; Claude Loverdo; Miran Park; Priyanna Ahsan; James O. Lloyd-Smith

The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. . https://doi.org/10.1101/066688 doi: bioRxiv preprint in strain frequencies could have disproportionate influence if host survival was short. Our work reveals the converse case, where strains with lower reproductive numbers at the epidemiological scale (in fact, less than one) can prevent evolutionary emergence if they have a within-host advantage, by causing the adapted strains to have a cross-scale reproductive number α of less than one. Consistent with our result, Lythgoe et al. [65] showed found that deterministic, multistrain models could produce equilibrium states dominated by strains that were competitively superior at the within-host scale, despite reducing the reproductive number at the epidemiological scale. Parallel to our finding that cross-scale conflict occurred only for long-term infections, Lythgoe et al. [65] 's short-sighted evolution was most pronounced when within-host dynamics occurred at a faster time-scale.