FCS) during entry (the first 2 h of infection) and were removed when the inoculum was replaced by growth medium containing BafA1. Concentrations up to 80 mM dynasore did not inhibit entry which is in agreement with the result shown in Fig. 1B . In contrast, 1.25 nM BafA1 already inhibited entry for more than 60% (Fig. 1F) . As a control, dynasore was also added at 2 hrs post infection to analyze whether the drug affected IAV replication during the post entry phase. As expected, 80 mM dynasore did not significantly inhibit IAV replication when present from 2 to 16 hrs p.i. (Fig. 1F ). Thus, with the Gluc-entry assay we can study the effect of specific inhibitors on IAV entry in a quantitative manner, at least as long as the inhibitors do not irreversibly affect IAV replication during the post entry phase.