Rotavirus particles, coloured transmission electron micrograph (TEM). Each virus particle consists of an RNA (ribonucleic acid) core surrounded by a triple layered capsid. Rotaviruses are probably the most common viruses to infect humans and animals. They are associated with gastroenteritis and diarrhoea - typically infecting the intestines of children aged from 6 months to 3 years. The viruses are spread in faeces. Magnification: x98,280 at 10 centimetres wide.