Positive strand RNA viruses usurp and modify cell membranes of different origins to replicate their genomes. (A) Mitochondrial membranes are targeted by Flock House Virus (FHV), which induces the formation of vesicles (white) at the outer mitochondrial membrane (blue); (B) 3D surface-rendered model of SARS-CoV–infected Vero E6 cells containing large double membrane vesicles (DMVs) (outer membrane, gold; inner membrane, silver) that remain connected to their source, the ER (in bronze); (C) Zippered ER, found in cells infected with the gammacoronavirus Infectious Bronchitis Virus (IBV), is connected to spherules (red arrows). DMVs (red arrowheads) are also found, but to a lesser extent; (D) Equine Arteriviruses (EAV) infection of HeLa cells results in the formation of DMVs (brown), depicting a core (blue) that is associated with the ER (beige) and close to ER tubules (green); (E) Closterovirus rearranges ER and mitochondrial membranes to form DMVs (red arrowheads) and vesicles packets (VPs) (red arrows); (F) Coxsackie B3 Virus (CVB3) usurps donor membranes most likely derived from the Golgi, appearing early in infection as single-membrane tubules (green), open (orange) and closed (yellow) DMVs and ER (blue); (G) 3D architecture of poliovirus membranous replication factories at intermediate stages of development, originating from cis-Golgi membranes. Single-membrane structures are depicted in different shades of blue. Note that these single membrane vesicles undergo secondary invaginations giving rise to DMVs at the late stages of infection; (H) Murine Norovirus 1 (MNV-1) infection results in the formation of vesiculated areas (VAs, red arrowheads) within aggregates of MNV-1 particles (red arrows). These VAs seem to originate from ER, trans-Golgi and endosomes; (I) 3D model of a cytopathic vacuole (CPV) found in Rubella Virus-infected cells. This CPV (yellow) is surrounded by the rER (light green) and contains a number of vacuoles, vesicles (white) and a rigid straight sheet (brown) that is connected with the periphery of the CPV. Mitochondria are depicted in red; (J) Typical cytoplasmic vacuoles induced by Semliki Forest Virus (SFV) in baby hamster kidney cells. Color code is as follows: blue-framed images depict single-membrane vesicle inducers; green-framed images correspond to double-membrane vesicle inducers. (The different parts were reproduced with permission: see acknowledgement section)