The disease has a wide geographical distribution, occurring in most, if not all, major Salmonids farming countries of North and South America, Europe and Asia, and has been reported from South Africa.

Viruses showing serological relatedness to IPN virus have been reported to cause diseases in some farmed marine fish species, such as yellowtail (Seriola quinqueradiata), turbot (Scophthalmus maximus) and halibut (Hippoglossus hippoglossus) and subclinical covert infections have been detected in a wide range of estuarine and freshwater fish species. Some of these viruses have been shown to cause IPN in Salmonids fry under experimental challenge conditions, but others do not

Disease reprinted courtesy of OIE Diagnostic Manual for Aquatic Animal Diseases, OIE (World Organisation for Animal Health), Paris, France.