The supernatant of the Kagoshima sample was subjected to virus isolation. The fecal supernatant was filtered through a 0.45-μm pore size membrane and treated with 10 μg/mL acetylated trypsin (Sigma-Aldrich, St. Louis, MO, USA) for 60 min at room temperature before virus isolation. Treated samples were inoculated into Mardin-Darby bovine kidney cells. Blind passage was subsequently conducted three times. Minimum Essential Medium was used as negative control (Sigma-Aldrich).