Single- and/or double-membrane viral factories?

Once entering the cell host, viruses needs to interact with intracellular membranes in order to build up their replication organelles or factories, resulting in a remodeling of the cell membranes, the hallmark of virus infection. Positive (+) strand RNA viruses represent the largest group of RNA viruses. Among them two different architectures of replication factories (morphotypes) have been described so far, differing mainly in the amount of lipid bilayers they have: one or two [1]. The single membrane morphotype consists in the formation of negatively curved membranes or invaginations towards the lumen of the host organelle, resulting in the formation of vesicles, vacuoles or spherules. This strategy is used by members of the families Nodaviridae, Bromoviridae, Togaviridae and Flaviviridae. The double-membrane morphotype involves the