Figure 2. Critical-drug efficacy, baseline HCV-RNA level and infection-rate constant, β.

We randomly chose one thousand parameter sets within the ranges given in Table 1, except p=0.1–6 virions/day (see Figure 1). We then calculated the critical-drug efficacy (ε_c) and virus steady-state level (V̄) using Eqs. (2) and (Eq. S3 in online supplemental material), respectively, for different ranges of the infection rate constant, β. These different ranges affect the percentage of hepatocytes that are HCV-infected, as shown in Table 3, - high fraction of infected cells (filled squares), moderately-high fraction of infected cells (filled circles), and moderate fraction of infected cells (filled triangles)). Here we plot the median ε_c in groups of in-silico patients that have baseline viral loads that differ by 0.5log₁₀ HCV-RNA IU/ml, and found that this median increases as a sigmoid function of baseline viral-load. Thus, higher baseline HCV-RNA levels correlate with higher median ε_c.