We also carried out ET of infected cells fixed at 4 days p.i.. At this time point the majority of cells exhibited heavily vesiculated membranes and produced rounded viruses of lower infectivity. The 3D analysis revealed that most viruses were roughly spherical in shape. They were generally found in close proximity to convoluted, vesiculating areas of the PM (figure 4A) and often surrounded by large numbers of cell-derived vesicles ( Figure 4A and Video S2). This suggests that release of spherical viruses occurs rapidly and simultaneously with the shedding of other cell-derived vesicles. NCs within spherical virions were bent or kinked but never broken or segmented, as might be suggested by 2D EM of thin sections (see, for example the 2D and 3D views of the spherical particle shown in Figure 4B ). None of the virus particles were toroidal, as has previously been suggested [39] . Interestingly, kinked NCs in spherical viruses had a total length of 734 nm, the same length as NCs in filamentous virions ( Figure 4B , Table 2 ) and they were associated along one side with the viral membrane ( Figure 4B ). These findings demonstrate that preassembled full-length NCs are packaged into each virion, irrespective of virus shape.