The Infectious Salmon Anemia Virus or Salmon Influenza is a viral disease that, as the name implies, causes severe anemia of infected fish. Unlike mammals, the red blood cells of fish have DNA and those cells can become infected with viruses. The anemia results in inadequate supllies of oxygen and the fishes develop pale gills and may swim close to the water surface, gulping for air.
Infection occurs mainly in Norway, Scotland, Canada, the USA and Chili in farmed trout and salmons. It causes high mortality among affected species. Subclinical infections have been recorded in herring, Atlantic cod and Pollock.
 Cottet et al: Infectious salmon anemia virus--genetics and pathogenesis in Virus Research - 2011
 Plarre et al: Evolution of Infectious salmon anaemia virus (ISA virus) in Archives of Virology - 2012