*2.4. Plaque-Forming Assay*

Viral titres were determined by a standard plaque-forming assay as previously described with minor modifications [31]. Briefly, Vero cells grown in a 48-well culture plate were infected with serial tenfold dilutions of virus samples for 2 h at 37 ◦C, and then incubated with 0.8% carboxymethylcellulose (CMC) for 4 days. Cells were fixed with 3.7% formaldehyde (FA) in PBS and stained with 0.5% crystal violet in 20% ethanol. Viral titres were expressed as plaque-forming units (PFU) per mL (PFU·mL−1).
