The monoclonal antibody (Mab) against Nodavirus (also know as VNN) is specific for this virus. The MAb has been tested by ELISA with Betanodavirus isolated from four different fish species, including European Sea Bass, Atlantic cod, halibut and Striped Jack.The Mab reacted with Nodavirus isolated from European Sea Bass that has been shown to belong to the RGNNV (red spotted groupe rnervous necrosis virus) cluster. It also reacted against Nodavirus isolated from Atlantic cod and halibut that have been shown to belong to the BFNNV (Barfin flounder nervous necrosis virus) cluster. The Mab did not react with SJNNV (striped jack nervous necrosis virus). SJNNV has been shown to be phylogenetically quite different to the other Nodavirus clusters.