The virus sinks deeper into the cell until it is completely wrapped up in cell membrane. The netlike structure beneath the docking virus and the whitish halo around the resultant vesicle represent clathrin, a protein that forms an external scaffold that causes the cell membrane to invaginate and finally form the vesicle. The clathrin coat is then lost and the virus in its naked vesicle can be seen half out of frame at the right of the image. It is more acidic in the endosome and this modifies the haemagglutinin spikes. The altered haemagglutinin draws the membranes of the virus and endosome together and they merge, creating a hole through which the viral contents are poured into the cytoplasm.
Some matrix protein is shown travelling to the nucleus .
The nucleocapsid segments, which contain the viral genetic information, migrate to the nucleus. Some matrix protein travels to the nucleus and some collects beneath the cell membrane. Production starts in the rough endoplasmic reticulum and progresses through the Golgi apparatus. These are then used to create further copies of the viral genome. These new -ve sense viral genomic RNAs become associated with nucleoproteins and some matrix proteins that have migrated into the nucleus.