Infectious Salmon Anemia (Isavirus) is a virul disease of Atlantic Salmon. This disease is listed as a non-exotic disease in the EU, and therefore is watched very closely. 

Pathology

As the name implies, it causes severe anemia of infected fish. The fish may develop pale gills, and swim close to the surface, gasping for air. Sometimes, the disease can even develop without showing any exterior signs of sickness. The fish maintain a normal diet, and then they suddenly die. Death rate in affected farms can also reach 100%. Upon examination, the causes of death can range from the liver and spleen being swollen, stopping of the circulatory system, and the blood may be contaminated with dead red blood cells. Isavirus seems to be most like the influenzavirus.