In the autumn of 1984, a new disease was observed in Atlantic salmon being farmed along the southwest coast of Norway. The disease, which was named Infectious salmon anemia, spread slowly. ISAV, a RNA virus, is the only species in the genus “Isavirus” which is in the family Orthomyxoviridae, it appears to be most like influenza viruses. Its mode of transfer and the natural reservoirs of infectious salmon anemia virus are not fully understood. By June 1988 it had become sufficiently widespread and serious to require the Norwegian Ministry of Agriculture, Fisheries and Food to declare it a notifiable disease.
ISA is a viral disease of Atlantic Salmon (Salmo salar) that affects fish farms in Canada, Norway, Scotland and Chile, causing severe losses to infected farms. The disease is listed as a non-exotic disease of the EU and is therefore watched closely by the European Community Reference Laboratory for Fish Diseases.
In Chile, ISA was first isolated from a salmon farm in the 1990s and described for the first time in 2001 although the initial presence never resulted in widespread problems. However, since June 2007, the national industry has been dealing with a serious ISA outbreak which has not yet been completely brought under control and has been responsible for an important decline in the industry, closure of many farms and high unemployment. In 2008 there has been an outbreak of ISA in Shetland.
There is no treatment once fish are infected.
Infectious salmon anemia is currently regarded as a serious threat not only to farmed Atlantic salmon, but also to dwindling stocks of wild Atlantic salmon. Recent research involving a multi-year study of wild Atlantic salmon from North America shows that infected salmon that survive infection generate antibodies against the virus. More about ISA: Wikipedia
We don’t know so far if after bird flu and swine flu there might be a salmon flu threatening humans in the near future. There are indications that this influenza virus can mutate and affect man.