Genetic map of the IHNV genome and cDNA clones used for sequence analysis. The location and relative size of the IHNV ORFs are shown; the numbers indicate the starts and ends of the respective ORFs. Six cDNA fragments (F1 to F6) were synthesized from the genomic RNA by RT-PCR. The primers used for RT-PCR fragments are shown at the end of each fragment. The RNA genome is 11,133 nucleotides long and contains a leader (L) and trailer (T) sequences at its 3'-end and 5'-end, respectively. The coding regions of N, P, M, G, NV and L genes are separated by intergenic sequences, which have gene-start and gene-end signals.