VHSV came from the marine environment: Clues from the literature, or just red herrings?

Viral haemorrhagic septicaemia (VHS) was for many years found only in fresh water fish, primarily the rainbow trout (Oncorhynchus mykiss), but the caus ative virus (VHSV) has now been isolated from an increasing number of marin e fish species. The marine fish may have been infected by virus from infect ed freshwater fish passing from rivers into the sea, but there is also the possibility that marine fish were the initial hosts of the virus, and it wa s passed from a marine reservoir to the freshwater environment by the feedi ng of marine fish to rainbow trout. Much of the latter hypothesis is specul ation. However, the early literature on the disease provides firmer ground to support that hypothesis; that literature is reviewed.