This Instruction determines the necessary measures for the identification, prevention and suppression of infectious hematopoietic necrosis of trout (Necrosis infectiosa haematopoetica salmonis) and viral hemorrhagic septicemia in trout (Septicemia haemorrhagica salmonis). Clinical signs for each disease are listed in Annex I of this text. Upon suspicion of the occurrence of any of the diseases listed in Annex I of this Instruction, the authorized veterinary organization is obliged to confirm or refute the suspicion without delay. Immediately after reporting a suspected disease, the authorized veterinary organization must: send freshly dead fish on ice or still alive fish suspected of being infected to laboratory examination; determine measures to prevent the spread of the disease with professional instructions; ensure harmless disposal of dead fish. The authorized veterinary organization must, immediately after reporting a suspected disease in a fish farm suspected of being infected, order: restriction of fish traffic; ensuring and maintaining suitable hygienic conditions in the fish farm.