Quantitative EM analysis of infected adherent cells that were fixed and embedded in situ revealed that cell morphology also changed over time. At day 1 p.i. 95% of the observed cells appeared intact and displayed filopodia-like PM protrusions ( Figure 1C , D). The cytoplasm often contained densely stained viral inclusions ( Figure 1D ) and virions were readily seen in the immediate periphery of cell profiles; they were easily identified by means of their electron-dense stain and a rod-shaped NC and were frequently found 'trapped' between or underneath adherent cells ( Figure 1E ). Over 90% of all observed virions around the cells were filamentous or hooked ( Figure 1F ). In contrast, when the monolayer was fixed at 4 days p.i., only 17% of the cell profiles were intact and 83% appeared vesiculated and resembled apoptotic cells ( Figure 1C , G). Most of the virus particles around such vesiculated cells were bent or round ( Figure 1F , H).