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

where b w and b m are the transmissibilities of the wild-type and the mutant, respectively. Here b w and b m account for the survival of the viruses through a range of processes during transmission, including their likelihoods of being shed from the donor host, surviving the environment outside of a host, and reaching and infecting the target cells in an uninfected host. Furthermore, as explained in the within-host model section, these parameters also account for the likelihoods of the viruses to survive initial local infection and establish a productive infection in the recipient host. Viruses may face different challenges and selection pressures to overcome the barriers in each of these processes. Here, for simplicity and generality, a single parameter is used to summarize the transmissibility of different viruses because little is known or measured about the ability of a virus to overcome these barriers. More explicit models can be constructed as the relevant data become available.