Table 1.

Differing genome organizations and replication strategies of RNA viruses

Virus family	Genome	Segmentation	Genome replication strategy	Protein expression strategy
Bromoviridae	Positive sense	Three segments	Makes negative-sense copies of segments	Makes genomic and subgenomic RNA (from an internal promoter)
Bunyaviridae	Negative sense	Three segments	Makes positive-sense copies of segments (the polymerase templates are RNPs)	Uses single-segment ORFs and then cleaves the resultant polyproteins
Coronaviridae	Positive sense	Unsegmented	Makes a negative-sense copy of the genome	Produces mRNA from genomic and subgenomic negative-sense RNA through discontinuous transcription
Flaviviridae	Positive sense	Unsegmented	Makes a negative-sense copy of the genome	Uses a single genome ORF and then cleaves the resultant single polyprotein
Retroviridae	Positive sense	Unsegmented (two copies)	Converts the genome to DNA, which integrates into the host genome	Uses the cellular machinery
Rhabdoviridae	Negative sense	Unsegmented	Makes a positive-sense copy of the genome (the polymerase templates are RNPs)	Processively transcribes each gene (the resultant mRNAs are not RNPs)
Togaviridae	Positive sense	Unsegmented	Makes a negative-sense copy of the genome	Makes genomic and subgenomic RNA (from an internal promoter)