Rotaviruses. Coloured transmission electron micro- graph (TEM) of a cluster of rotaviruses. They are probably the most common viruses to infect humans and animals. Rotaviruses get their name from their wheel-like appearance, with a rounded core and radiating spikes of the outer protein shell. They contain RNA genetic material. These viruses are associated with gastroenteritis and diarrhoea in humans and other mammals. Typically they infect the intestines in children of age 6 months to 3 years. The diarrhoea results in fluid loss and dehydration, and the viruses are spread in faeces. Magnification: unknown.