Fig. 2. By TEM, SARS-CoV-2 virions are discernible by the punctate pattern of the nucleocapsid containing lumen and often the presence of a S glycoprotein coat.

a Virions are seen extracellularly at the cell surface and intracellularly within viral-containing compartments. In some compartments, virions were observed without an S glycoprotein coat. b In comparison, endosomes consist of intraluminal vesicles that are smaller, lighter in appearance, and lack the nucleocapsid punctate interior of virions. c The three different lineages (B.1.1.7, B.1.258, and B.1.117.19) have a similar ultrastructural appearance by TEM. d A clathrin-coated vesicle can be discerned from a virion by having a denser coat that viral S glycoprotein and lacking punctate nucleocapsid in the interior. e There was no statistical significance in the diameter of virions (N = 23), the distance of virions from the host plasma membrane (N = 26), or the number of S glycoprotein projections on the viral surface (N = 25). This was determined using paired, two-tailed Student’s t-tests. Data were presented as mean values ± SEM. Scale bars (a–d) 100 nm.