In order to better harness future antiviral therapies, Kim et al. investigated SARS CoV-2, MERS-CoV and SARS-CoV dynamics within infected hosts. Through mathematical modelling, investigators found that SARS CoV-2 reproduces at a faster rate at the time of symptom onset, as compared to MERS-CoV and SARS-CoV. The interval between symptom onset and peak viral load was also shorter for SARS-CoV-2 (2.0 days vs. 12.2 for MERS-CoV and 7.2 for SARS-CoV). Consequently, efficacy of future antivirals will differ depending on their mechanism of action. For example, antivirals that block de novo infection or virus production are likely to be effective only if administered before viral load peak. The timing of antiviral administration may be less relevant for cytotoxic antivirals. Combination antiviral mechanisms (e.g., de novo blocker and cytotoxic) will likely yield the greatest effect at reducing viral load.