Model of the reovirus egress machinery . VIs contain membranes and filaments that are bound to mature virions. Lysosomes are recruited to VIs and become SOs, which collect mature virions likely by a filament-dependent mechanism. When virions become densely packed inside SOs, smaller MCs bud from the SOs. MCs move to the cell periphery, fuse with the plasma membrane, and release virions into the extracellular medium.