In a hatchery on the Hallwilersee, a medium-sized lake in Switzerland, occurred a loss of about 120,000 pike fry during a 7-day period. The very acute course of the disease with a mortality nearly 100% was impressive. Widespread hemorrhages in the skin and the muscles and exophthalmus were the most important signs. At post-mortem hemorrhages were observed retroperitoneally and around the kidney.
Virological investigations and infection experiments with the pike virus and fresh isolated Egtved virus strains (originating from rainbow trout) to pike and rainbow trout established the Egtved-Virus as the cause of the disease.