TABLE 1.

Main characteristics of the Astroviridae family

Characteristic
Virion structure
Icosahedral particles, 28–41 nm in diam
Nonenveloped
Distinctive five- or six-pointed star-like shape under the electron microscope in about 10% of the virions
Genome
A single molecule of infectious, positive-sense ssRNA, 6.4–7.7 kb, with a poly(A) tail
Three ORFs: ORF1a and ORF1b at the 5′ end encoding the nonstructural proteins and ORF2 at the 3′ end encoding the structural proteins
VPg protein linked to the 5′ end
A ribosomal frameshifting signal present between ORF1a and ORF1b
Lack of a helicase domain
Replicative cycle
Structural proteins are expressed from an ∼2.8-kb subgenomic RNA