2.4. PCR amplification of S gene
The complete S gene was PCR-amplified from samples already known to be FCoV-positive according to the primers in Table S1. All PCR products were purified using the Omega Gel Kit following the manufacturer’s instructions. They were ligated to the pMD19-T vector (TaKaRa Bio Inc.) and transformed into DH5α competent Escherichia coli cells for sequencing. The S sequences were assembled using SeqMan software (version 7.0; DNASTAR).