An efficiency of plaque formation assay was performed with the indicated viruses in Vero cells and SH-SY5Y cells. Confluent monolayers of cells were infected with serial ten-fold dilutions of virus at 32°C, overlaid with semisolid growth media, and then incubated for five days at 32, 35, 36, 37, 38, or 39°C. Plaques were visualized by immunostaining and quantitated. The limit of detection (100.7 PFU/ml) is indicated by a dashed line.