Fig. 1

Schematic presentation of the within-host infections processes and their relation to transmission parameters. At the within-host level, viral replication and immune responses race with each other that eventually determines an individual infectivity, for example, his symptoms and possibly behaviours. At the between hosts level, infected individuals make contact(s) with susceptible individual(s) that eventually lead to a transmission, depending on both the infectivity of the infectious and the susceptibility of the susceptible. Noting that while the contact network can be fixed, the portion actively partake in epidemic spreading dynamically change over time [75]