Notes on Family: Mesoniviridae

enveloped spheres
enveloped spheres


General Description

This family consists of insect-infecting nidoviruses and is placed in the order Nidovirales, together with the families Arteriviridae, Coronaviridae and Roniviridae. Its name reflects the fact that the genomes in this family are intermediate (Greek, meso = medium) in size between the small arteriviruses and the large corona- and roni-viruses.


Virions are enveloped spheres about 60-80 nm in diameter.


Monopartite positive sense single-stranded RNA about 20kb long and with a 3'-polyA tail. Two large, overlapping ORFs at the 5'-end of the genome encode the major non-structural proteins and are expressed as a fusion protein by ribosomal frameshift. Downstream are at least 4 other genes, mostly or entirely encoding structural proteins, and these are probably expressed from a 3'-coterminal nested set of subgenomic RNAs.

Genera in the Family

There is currently only one genus: