Virions (virus particles) of the rotavirus, double-shelled. Individual virions consist of a protein capsid surrounding a core of double-stranded RNA. Rotaviruses belong to the Reovirus class, whose members possess icosahedral symmetry, are 65-75 nanometers in size and are non-enveloped. Other members of virus families are surrounded by alipoprotein envelope that is often derived from the host cell's membranes. The rotavirus causes infective diarrhea, especially in children and the elderly.