Transmission electron micrograph of rotaviruses. These belong to the genus Reovirus, and are the causative agent of infantile gastroenteritis in humans, mice and calves. The viruses are between 70nm and 75nm in diameter, and do not have the lipoprotein envelope seen in many other genera. The genome of this virus is a double-stranded RNA, fragmented into ten segments. The virus gets its name from the wheel-like appearance of the capsid (protein shell). Magnification: x340,000 at 6.5\ x 8.5\" size."