Translocation of the virion or its genetic material from the extracellular space into the host cell cytoplasm. Entry is achieved through pore formation, membrane fusion and/or endocytosis mechanisms.
Penetration reactions occur mainly in five locations: the cell
membrane, early and late endosomes, caveosomes, and the ER. Many viruses are able to utilize multiple uptake pathways, simultaneously, or depending on the host cell type targeted.