Researchers led by a Canadian government scientist have diagnosed potential heart and skeletal muscle inflammation in farmed salmon from British Columbia province, the Canadian fisheries ministry announced on Friday.
The disease, detected in samples collected from an aquaculture facility in 2013-2014, affects fish but poses no risk to human health.
To date, it has not been found in wild Pacific salmon.
First observed in Norway about 25 years ago, it led to significant production problems at affected farms, causing death in up to 20 per cent of stocks, said lead researcher Kristi Miller of Fisheries and Oceans Canada.
Fish farms have regularly had to fight viruses as their high concentrations of fish provide a fertile environment for the spread of parasites and disease.
Last decade, sea lice decimated salmon populations in fish farms in Norway. In Chile, infectious anemia also caused significant mortality in farmed Atlantic salmon.