A polymerase chain reaction (PCR)‐based assay to detect nervous necrosis virus (NNV) in fish was developed by using two sets of primers designed on a highly conserved region of the coat protein gene encoded by RNA2 of NNV. The first pair of primers amplified a fragment of 605 bp by one‐step reverse‐transcription (RT)‐PCR, while the second pair amplified an internal segment of 255 bp by nested PCR. Addition of nested PCR increa...