The lipid bilayer envelope carries 3–4 structural proteins. (i) Membrane (M) proteins are the most abundant small triple-spanning transmembrane proteins that define the virion morphology and are major coordinators of virion assembly [140]. (ii) Envelope (E) proteins are minor channel-spanning transmembrane proteins that work together with the M proteins for virion assembly, budding and release [141]. (iii) Spike (S) proteins are homotrimeric type I transmembrane glycoproteins [142] protruding from the virion envelope (20 nm in length) that resemble a crown (Latin: corona) under an electron microscope.