Viral haemorrhagic septicemia and infectious hematopoietic necrosis

Viral haemorrhagic septicemia (VHS) and infectious hematopoietic necrosis (IHN) are virus diseases causing heavy losses in salmonids. Norway currently has a free status for both diseases.

Both diseases are due to infection with Novirhabdovirus and are listed nationally and internationally. The VHS virus is also detected in several marine species including lumpfish and wrasse.

The purpose of the surveillance program is to document the free status for VHS and IHN in salmon and rainbow trout in Norway.

2025

This surveillance programme has a risk-based approach. The core surveillance activity is the routine clinical inspections on sites with farmed salmonids and analyses of samples collected from diseased fish. Samples from rainbow trout and brown trout from freshwater sites are also included. Infectious haematopoietic necrosis virus and viral haemorrhagic septicaemia virus were not detected in any of the samples tested in 2025.

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