Cripaviruses are a genus of + sense, single-stranded RNA (ssRNA) viruses. If a ssRNA virus is +sense, it means that the viruses can produce proteins directly from their RNA genome upon entering a cell; and therefore, may not require an RNA polymerase packaged in with it, as this may be produced from the genome after entering the cell.

The genome

Genome

In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....

 is 8500–9500 nucleotides long, and has a VPg

VPg

VPg is a protein attached to the 5' end of RNA during RNA synthesis in a wide variety of viruses including Picornaviridae such as Foot-and-mouth disease and poliovirus . VPg stands for "viral protein genome-linked".-Attachment during RNA synthesis:...

 (genome linked viral protein) on the 5' end. The 5' end also has a series of C's near it, while the 3' end has a series of A's near it.

These viruses have capsid

Capsid

A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic...

s of 12 capsomers but no envelope

Viral envelope

Many viruses have viral envelopes covering their protein capsids. The envelopes typically are derived from portions of the host cell membranes , but include some viral glycoproteins. Functionally, viral envelopes are used to help viruses enter host cells...

, and are round 27–30 nm in diameter with an icosahedral

Icosahedral symmetry

A regular icosahedron has 60 rotational symmetries, and a symmetry order of 120 including transformations that combine a reflection and a rotation...

 symmetry.

The name of the cripavirus family originates from its most famous member the Cricket Paralysis Virus. Which was made famous by its rather unique IRES (Internal Ribosome Entry Site): the Cripavirus IRES

Cripavirus internal ribosome entry site (IRES)

The Cripavirus internal ribosome entry site is an RNA element required for the production of capsid proteins through IRES-mediated translation....

. The Cripavirus IRES is an RNA element that allows the virus to bind the ribosome and translate without a need for any initiation factors – as initiation is the most regulated step of translation this allows the virus to avoid many mechanisms to inhibit viral activity.