Total RNA from mock or virus-infected MDCK cells was collected at 18hpi and purified using TRIzol reagent according to the manufacturer’s specifications. The cDNAs were synthesized using superscript® II Reverse Transcriptase (Invitrogen) and an oligo-dT primer to amplify total mRNAs (mCherry and GAPDH); or specific primers for the NS and NP vRNAs. The cDNAs were used as templates for semi-quantitative PCR with primers specific for the NS and the NP vRNAs and for the mCherry and canine GAPDH mRNAs (available upon request).