Viruses with positive-sense ssRNA genomes
Coronaviridae
With the Aretriviridae, forms the order Nidovirales. Enveloped particles of 120 to 160 nm with club-shaped sparse protein spikes. Contains a helical nucleocapsid with one molecule of positive-sense ssRNA of 28000 to 31000 nucleotides. one of the largest RNA genomes. CIytoplasmic replication with a nested set of subgenomic mRNAs with a common leader sequence. Buds from Golgi apparatus and endoplasmic reticulum.