Rotavirus structure, illustration. Rotaviruses are non-enveloped viruses, and have a triple-layered protein coat (capsid) structure. Within the capsid are eleven segments of double-stranded ribonucleic acid (RNA, middle). Rotaviruses are one of the most common viruses to infect humans and animals, typically affecting children aged from 6 months to 3 years. They are associated with gastroenteritis and diarrhoea, through infecting cells of the small intestine (intestinal projections, or villi, are blurred in the background, pink). They are spread through faeces.