Rotavirus particles. Coloured transmission electron micrograph (TEM) of rotavirus particles (orange). They are named after their wheel-like appearance, with a rounded core and radiating spikes on the outer protein shell. They contain ribonucleic acid (RNA) genetic material. Rotaviruses cause gastroenteritis and diarrhoea in humans, commonly infecting the intestines of young children aged 6 months to 3 years. The diarrhoea results in fluid loss and dehydration, and the viruses are spread in the faeces. Magnification: x136,000 when printed 10 centimetres wide.