Joshua C. Macdonald, Hayriye Gulbudak, Brianna Beechler, Erin E. Gorsich, Simon Gubbins, Eva Pérez-Martin and Anna E. Jolles

We investigated within-host dynamics and among-host transmission of three strains (SAT-1, -2, -3) of foot-and-mouth disease viruses (FMDVs) in their wildlife host, African buffalo. Our data reveals contrasting within-host dynamics among viral strains, with SAT-2 eliciting more rapid and effective immune responses than SAT-1 and SAT-3. Within-host viral fitness was overwhelmingly determined by variation among hosts in immune response activation rates but not by variation among individual hosts in viral growth rate. Our analyses investigating across-scale linkages indicate that viral replication rate in the host correlates with transmission rates among buffalo and that adaptive immune activation rate determines the infectious period. These parameters define the virus’s relative basic reproductive number (ℛ₀), suggesting that viral invasion potential may be predictable from within-host dynamics.

American Naturalist. July 2024