Synergy plots, which reveal the extent of synergy at each concentration of each drug in the combinations, are shown in Figures S1 for CA05. The data are presented as contour plots, in which regions where inhibition is greater (synergy) or less (antagonism) than expected are identified by subtracting the theoretical additive inhibition from the observed inhibition. Synergy plots for TCAD regimen showed a concentrationdependent increase in synergy with respect to amantadine ( Figure S1B , top plane). At the highest concentration tested (3.2 mg/mL), synergy was observed over a wide range of concentrations of ribavirin and oseltamivir carboxylate tested. At lower concentrations of amantadine, synergy occurred at 1 mg/mL ribavirin and higher, and at 0.0032 mg/mL oseltamivir carboxylate and higher. No significant antagonism was observed at any dose of any drug in the double combinations or the TCAD regimen. Similar patterns of synergy were observed with double and triple combinations of these antiviral drugs against CA04 and CA10 (data not shown).