We next investigated the mechanism(s) by which compound L3 inhibited flaviviruses and showed that compound L3 reduced DENV-1 (at 36 h), DENV-2 (at 30 h), and ZIKV (at 36 h) infection in MCF-7 cells by decreasing HER2 activity and further inhibiting the phosphorylation of the HER2 downstream molecules Src and ERK1/2, thereby suppressing viral protein expression and viral titers (Figure 4A–F). Here, ERBB2 is linked to infection.