FIGURE 2.

Thin‐section electron microscopy images show the various development stages of coronaviruses in the human fetal diploid lung (HDFL) cells 24 hr after infection. Part figure (a) shows that coronaviruses are in the cisternae of the endoplasmic reticulum of a cell (part of cytoplasm). Part figure (b) shows that coronaviruses are in the perinuclear spaces in a cell. The virus particles are in spherical shape and its diameter ranges from 80 to 160 nm. Part figure (c) shows the formation of six particles inside a vacuole in the cytoplasm in various stages of budding process formation. Part figure (d) shows a tubular structure containing a dense material in cytoplasmic inclusion. Part figure (e) illustrates the relationship of virus particles to a cytoplasmic inclusion composed of tubular structures. Arrows in the figure point to structures of developing virus particles which also resemble the tubular structures of the inclusion. Part figure (f) shows that the cytoplasmic inclusion is composed of densely staining material around the tubular membrane. Source: This figure is adapted with permission from Oshiro et al. (1971)