Subgenomic mRNAs are essentially smaller sections of the original transcribed template strand.
[1] Positive-sense (5' to 3') viral RNA which may be directly translated into the desired viral proteins, undergoes a similar process as described in 3' to 5'.
Portions of the viral RNA may be skipped during translation.
Or, different proteins can be created with positive sense viral RNA.
[2] This complex method of transcription is generally restricted to viruses, especially those of the single-stranded, positive-sense RNA or Class IV viruses using the Baltimore Classification System, e.g. viruses of the order Nidovirales.