Plaque assays were performed as previously described [19] to characterize plaque morphologies. Briefly, after absorption of PEDVs at an MOI of 0.0001, confluent monolayers of Vero cells in six-well plates were washed twice with DPBS and then covered with an overlay of pre-warmed PI medium containing 1% agarose. After solidification of the overlays, the plates were incubated at 37 °C for 72 h to produce distinct plaques. The cells were then fixed in 3.16% neutral-buffered formalin for 1 h before removing the semisolid overlays. The plates were stained with 1% crystal violet in 20% ethanol and distilled water for 1 min. Viral plaques were inspected after washing off the crystal violet solution, rinsing the plates with water, and air-drying at room temperature (RT).