Relative quantification of SAV in water samples from tanks containing PD vaccinated or unvaccinated fish. Fold changed mean normalized expression (MNE) values from Ct values obtained from water samples by qRT-PCR. Ct values (mean of triplicate) obtained for the nsP1 assay (target) were normalized against Ct values obtained for the ISAV spike (reference). Subsequently, all MNE values were calibrated against the lowest MNE value obtained from water samples (fold change). Tanks 1 and 2 contained AQUAVAC® PD7 vaccinated fish (n = 60 per tank), while tanks 3 and 4 contained unvaccinated fish (n = 60 per tank). All four tanks contained naïve cohabitants (n = 10 per tank) from 1 dpc.