Nucleic acid extraction and cDNA synthesis
Viral nucleic acid was extracted from 200μl of each stool supernatant using the MiniBEST Viral RNA/DNA Extraction Kit (TaKaRa, Japan), and the obtained nucleic acid was then reverse-transcribed to synthesize cDNA using Transcriptor First Strand cDNA Synthesis Kit (Roche, Switzerland) in accordance with the manufacturer’s instructions. The cDNA was used as the template directly for polymerase chain reaction (PCR) or kept frozen at -20℃.