Effective surveillance for early classical swine fever virus detection will utilize both virus and antibody detection capabilities.

•Effective CSFV detection will require a combination of virus- and antibody-based detection methods.•CSFV RNA was detected in oral fluid from infected pigs by rRT-PCR before the appearance of clinical signs.•Differences in diagnostic sensitivity were observed among the rRT-PCRs and assay performance was also affected by CSFV strain.