Class 4: Single-stranded RNA viruses - positive-sense 
edit 
Positive-sense RNA viruses, along with all genes categorized as positive-sense, have the capability to be directly engaged by host ribosomes, leading to immediate protein synthesis.Class 5: Single-stranded RNA viruses - negative-sense 
edit 
Negative-sense RNA viruses, along with all genes classified as negative-sense, cannot be directly utilized by host ribosomes to synthesize proteins instantly.