Try to keep up Chris. As you will see below, PRV has been here a long time.
"Salmonid tissues tested for PRV by real-time rRT-PCR included sections from archived paraffin blocks from 1974 to 2008 (n = 363) and fresh-frozen hearts from 2013 (n = 916). The earliest PRV-positive sample was from a wild-source steelhead trout, Oncorhynchus mykiss (Walbaum), from 1977. Archived paraffin samples from 1974 to 1994 were from the histology laboratory of the Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada. Blocks were selected to include a range of years and a mixture of farmed salmon and salmonids sampled from the wild or from enhancement hatcheries. Records related to many of these samples are incomplete, but in all cases, the year of sample collection is known. In some cases, tissues from a single fish seem to be distributed in more than one paraffin block, but these records are also unclear; therefore, prevalence for these samples is based on the known number of paraffin blocks rather than the unknown number of fish. As an estimate of the preservative that was used, tissue colouration was recorded when the paraffin sections were processed for rRT-PCR analysis: yellow (probably Bouin's fixative) or normal (probably Davidson's fixative); during these years, the Pacific Biological Station did not use 10% neutral buffered formalin (W. Bennett, DFO, personal communication)."