Torovirus structure, illustration. Toroviruses have a doughnut-shaped structure consisting of an outer envelope (dark blue) with spike proteins (yellow). This encloses a helical nucleocapsid (protein coat, pink) that wraps around its single-stranded ribonucleic acid (RNA, blue) genome. They primarily infect vertebrates, such as pigs, horses, and cattle, likely spread through faeces. Toroviruses commonly cause diseases like diarrhoea and gastroenteritis.