Nidovirales

Nidovirales is an order of enveloped, positive-strand RNA viruses which infect vertebrates and invertebrates. Host organisms include mammals, birds, reptiles, amphibians, fish, arthropods, molluscs, and helminths. The order includes the families Coronaviridae, Arteriviridae, Roniviridae, Tobaniviridae, and Mesoniviridae.

Member viruses have a viral envelope and a positive-sense, single-stranded RNA genome which is capped and polyadenylated. Nidoviruses are named for the Latin nidus, meaning nest, as all viruses in this order produce a 3' co-terminal nested set of subgenomic mRNAs during infection.