Unlimited supply of antiviral drugs. Required stockpile of antiviral drugs (relative to S
0) as a function of R
0 with a constant treatment level of: (a) 20%; (b) 40%; and (c) 60%. Ratio of the total number of clinical infections to S
0 as a function of R
0 with a constant treatment level of: (d) 20%; (e) 40%; and (f) 60%. Solid curves correspond to the case where resistance is absent, and dashed curves represent the scenario in which resistant viruses with HTF are present.