Nidovirales is an order of viruses with animal and human hosts (MERS-CoV and SARS-CoV). It includes the families Coronaviridae, Arterivirus,Roniviridae and Mesoniviridae.
The order Nidovirales is named for the Latin nidus, meaning nest, as all viruses in this order produce a 3' co-terminal nested set of subgenomic mRNA's during infection.