Fig. 2.

Crystal violet stained plaque assay plates. Vero-furin or Vero E6 cells were inoculated with 10-fold serial dilutions of a SARS-CoV-2 stock. Plates were fixed three days post-infection and stained with crystal violet. Wells with individual plaques were used to determine the virus titer (Vero-furin 10⁻⁴, Vero E6 10⁻³). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)