Betanodavirus, also known as nervous necrosis virus, is a viral genus present in the family of Nodaviridae. It has been separated into 4 clusters: Striped Jack nervous necrosis virus (SJNNV), Tiger puffer nervous necrosis virus (TPNNV), Barfin flounder nervous necrosis virus (BFNNV) and Red-spotted grouper nervous necrosis virus (RGNNV). An additional genotype named turbot Betanodavirus strain (TNV) has also been proposed. These Betanodaviruses are non-enveloped viruses with a single-stranded positive sense RNA genome and are known to affect more than 120 species of farmed and wild fish. Diseases caused by Betanodaviruses are commonly known as viral encephalopathy and retinopathy (VER) and they damage the central nervous system in susceptible fish species, typically (but not always) in the younger stages of life. Infectedlarvaeoftendisplayabnormalswimmingbehavioursincludingspinning,flexingofthe body, vertical positioning and muscle tremors. These diseased fish are primarily found at the surface due to hyperinflation of the swim bladder. Changes in skin pigmentation may also be seen. However, these behavioural changes can also be caused by other infections or environmental factors. One way to be sure of Betanodavirus infection is to perform. Real time PCR is therefore very beneficial in such a situation in order to achieve fast and accurate results.