frame 1 - post endocytosis, but pre-acidification change in the endosome

frame 2 - post-H change in the endosome, glycoprotein E is now erect & freely diffusing in the plane of the viral membrane

frame 3 - glycoproteinE inserted into the endosomal membrane (pre folding-back & fusion)

frame 4 - endosome & virial membranes are fused, viral RNA is released into the cytosol