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

Cross-scale selection and the mutant reproductive number R m . The reproductive numbers of the wild-type strain (R w ) and mutant strain (R m ) can be calculated as the product of the contact rate, the average transmissibility of the strain during the infectious period, and the infection duration (see, Coombs et al. [73] and Appendix). These reproductive numbers are positively correlated with the contact rate, infection duration, transmissibility, and viral per-capita growth rates. The influence of the maximal viral load K depends on the infection duration. For short-term infections, defined here as infections with a relatively short saturated phase (i.e. T − T e T e ), increasing K has little effect on a strain's reproductive number. For long-term infections, defined here as as infections with a long saturated phase (i.e. T − T e T e ), reproductive numbers increase with K.