Toroviruses

Toroviruses are a genus of enveloped, positive-sense single-stranded RNA viruses in the subfamily Torovirinae of the family Coronaviridae, order Nidovirales. They infect mammals and are best known for causing gastroenteritis in livestock and humans. The virions are roughly 80–100 nm in diameter and have a helical nucleocapsid enclosed by an envelope with surface glycoproteins.

Toroviruses carry a large RNA genome, about 27–30 kilobases, with a 5' cap and 3' poly(A) tail. Organization resembles other nidoviruses, including a sizeable replicase region (ORF1a/1b) followed by genes for virion proteins such as spike (S), membrane (M), and nucleocapsid (N).

Transmission is primarily fecal-oral, and infections are associated with enteritis. In animals, Breda disease of calves is caused by a bovine torovirus; equine and porcine toroviruses have also been described. Human torovirus has been detected in stool and linked to sporadic gastroenteritis cases, especially in children, though it is not considered a major global pathogen.

Diagnosis relies on molecular methods such as RT-PCR, with electron microscopy and serology as ancillary tools. No widely used vaccines exist, and control focuses on hygiene and sanitation.

Taxonomically, Torovirus is a genus within Coronaviridae, subfamily Torovirinae. Ongoing research continues to define species boundaries and disease associations.