Torovirus

Torovirus
Virus classification
Group:	Group IV ((+)ssRNA)
Order:	Nidovirales
Family:	Coronaviridae
Subfamily:	Torovirinae
Genus:	Torovirus
Type species
Equine torovirus

Torovirus is a genus of viruses in the order Nidovirales, in the family Coronaviridae, in the subfamily Torovirinae. They primarily infect vertebrates., especially human, cattle, pig, and horse. There are currently four species in this genus including the type species Equine torovirus. Diseases associated with this genus include: gastroenteritis, which commonly presents in mammals, but rarely in humans.

Torovirus particles share characteristics with other members of the Coronaviridae family; they are round, pleomorphic, enveloped viruses about 120 to 140 nm in diameter. The virus particle has surface spikes proteins that are club-shaped and are evenly dispersed over the surface. A nucleocapsid that is doughnut-shaped with helical symmetry is present.

Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment of the viral S protein (maybe also HE if present) to host receptors, which mediates endocytosis. Replication follows the positive stranded RNA virus replication model. Positive-stranded RNA-virus transcription, using the premature termination model of subgenomic RNA transcription is the method of transcription. Translation takes place by -1 ribosomal frameshifting. Human, cattle, pig, and horse serve as the natural host. Transmission is thought to be via the faecal-oral route.

Toroviruses are class IV viruses, and have a single piece of single-stranded, positive-sense RNA. The total length of this is about 28,000 nucleotides and, like all members of the Coronaviridae, toroviruses have a complex replication mechanism that includes the use of subgenomic mRNA, ribosomal frameshifting, and polymerase stuttering.

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