Rotavirus particles. Coloured transmission electron micrograph (TEM) of rotavirus particles (green and yellow). They are named after their wheel-like appearance, with a rounded core and radiating spikes of the outer protein shell. They contain 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 faeces. Magnification: x250,000 when printed 10 centimetres wide.