<Li> Endocytosis: The host cell takes in the viral particle through the process of endocytosis, essentially engulfing the virus like it would a food particle . </Li> <Li> Viral Penetration: The viral capsid or genome is injected into the host cell's cytoplasm . </Li> <P> Through the use of green fluorescent protein (GFP), virus entry and infection can be visualized in real - time . Once a virus enters a cell, replication is not immediate and indeed takes some time (seconds to hours). </P> <P> The most well - known example is through membrane fusion . In viruses with a viral envelope, viral receptors attach to the receptors on the surface of the cell and secondary receptors may be present to initiate the puncture of the membrane or fusion with the host cell . Following attachment, the viral envelope fuses with the host cell membrane, emptying the now - bare virus into the cell . In essence, the virus's envelope "blends" with the host cell membrane, releasing its contents into the cell . Obviously, this can only be done with viruses that have an envelope (examples of such enveloped viruses include HIV and herpes simplex virus .) </P>

How are viruses able to recognize a host cell and enter it